1) Listen to Your Coach
I used to be a Project Manager (among other things) in the video game industry. Did it for many years and as the teams I worked with got bigger and bigger, communication became more and more important. It was a relatively fluid environment with changes always coming down the pipe - dates, assignments, features, etc. We'd have meetings and send out emails but people wouldn't always get the message. Then they'd get mad when they didn't know what was going on. I tried very hard to impress on them that communication is a 2-way street. Information must be broadcast and information must be received. Just broadcasting doesn't mean something gets communicated. The receiver must actively receive it. They must pay attention and process it.
Of course this is true in everything else and certainly boxing. Listen to what your coach is broadcasting, even if you think it doesn't apply to you or you already know it.
2) No Really, Listen
When it comes to learning a skill like boxing, especially at a furious pace when you are tired, it is easy to become unaware of what you are actually doing. A couple years ago, if a coach would have told me to keep my hands up when I was punching, I would have thought, "Duh, I'm already doing that!" But the strange thing was, I wasn't. I thought I was but I wasn't always. This is VERY common and a big reason why we all need coaches. We tend to think we are doing something but an impartial observer will notice otherwise. We have to be willing to always question ourselves and accept feedback.
3) Don't Assume That You Can't Do It
This is huge. I have now seen many thousands of people learn to box, many of them not necessarily young, athletic, fit or have a natural aptitude for learning a sport. These things do not have to be barriers though. True, everyone progresses at different rates but everyone CAN do it and everyone can be stronger and faster than they currently are.
The problem, though, is not physical at all. It's mental. I can usually tell from looking at someone whether or not they believe they can do something I've asked them to do. And it is pretty much as simple as is this: if they think they can, they can. If they think they can't, they can't. The mental barriers are just as strong as the physical ones. Too often, I see folks resign themselves to believing something is too hard and they can't do it right off the bat instead of calmly, taking each part step by step and executing with confidence. Believe that you can do it, believe that you can do better, and both things will be true.
4.) But Don't Assume That You've Got It Either
This is kind of the flipside of #3. Believing that you've got something down and no longer need to think about making it better anymore. Whether it is boxing or any sport, the highest level athletes don't practice less than everybody else because they are so good, they practice more! There is never a point where a boxer says something like, "I don't think I need to practice throwing jabs any more. I've thrown millions and that jab is as good as it's going to get." No, your jab and your everything can ALWAYS get better. That is a great thing about sports. There are no ceilings!
5.) You Must Push and Get Uncomfortable
I have met plenty of people who say they want to get better but they want this to somehow happen magically or without putting in harder work than they have put in previously. Unfortunately, as nice as it would be, this is not going to happen. We all have to ask ourselves, do we really want to get better? Really? Or are we just telling ourselves this because they alternative sounds negative?
If you really want to get better at boxing (or most things in life), you're gonna have to work for it. You are going to have to leave your comfort zone, physically and mentally. You can't be afraid to push yourself a little harder when you're completely exhausted and just want to rest. You can't be afraid to try something brand new that you might look silly doing. You can't be afraid to change something that you've been doing for a long time and is awkward to fix. Even if you are boxing only for fitness, don't be afraid to slow down and try to get some of the mechanics right. You may feel like you are sacrificing your workout that particular day but in the long term, your workouts will improve with proper technique. There are lots of ways to get out of our comfort zone and we have to do pretty much all of them to get better! Doing the same thing over and over will not get you there.
This also relates to working on the things you have more trouble with. If you struggle with something like, say, uppercuts, don't just resign yourself to the fact that you struggle with uppercuts. Work extra hard on them and be comfortable being uncomfortable. Just like you push past the physical barriers, you must push past those mental barriers too.
6.) Stay Disciplined When You Are Tired
Speaking of scary things, getting really tired during a workout is kind of scary. We don't usually think about it in those terms but it is true. Being tired at the end of a long day and climbing into a comfy bed is great but the kind of physical exhaustion that comes from a high-intensity workout is a whole different animal. What's more is that when you feel this way and the workout is not even half over. You have to still go on, despite wanting very much to stop.
If/when this happens to you, what if you looked at it in a totally different way? What if you looked it at as A) a good sign that shows you are working hard and making yourself stronger (despite feeling weaker at that exact moment) and B) see it as an opportunity to stay disciplined? If you watch just about any boxing match that goes into the later rounds, you will see professional boxers in the best physical condition possible start to get tired. For many of them, when they get tired like this, things start to change. They're not as up on their toes, their hands aren't always up, their punches don't snap like they used to, etc.
Some of that is certainly inevitable but if you find yourself feeling tired and not as sharp as you once were, start to focus more on what you are doing. Work extra hard to keep your hands up, stay on the balls of your feet and if your punches aren't as snappy, throw fewer of them, but focus more on snapping the ones you do throw. It really doesn't save you that much energy to put your hands down and rest than if you had just kept your hands up and moved around the bag. The difference is much smaller than someone might think. So do it! Spend that extra joule of energy, as I like to say, staying disciplined.
7) Finish Strong!
Let's say you're not having the greatest day of training ever. Maybe you're tired and you're sick of trying to stay disciplined and you're pushing yourself but just feel like you are grinding your gears. We all have those days. All of us. Pro boxers even take rounds off sometimes! But in training, I would never advise taking a round off. What you can do though, is slow things down for a round where you're grinding a little bit but still try to finish strong at the end of the round. Or end of the session. Give yourself that extra push at the end because you know a break is coming. It won't feel great and you won't want to do it but it will make a big, positive difference in the long-term. Plus it trains your body to recover better and creates somewhat of a killer instinct.
8) Film Yourself
I mentioned earlier about how a coach can see things you can't and it's important to listen to them but sometimes, YOU need to see it to believe it. I also mentioned earlier not believing that I was dropping my hands on punches until I finally saw video of me doing it.
So film yourself during a boxing training session and then watch it back later. WARNING! You might be taken aback by what you see. Besides technical mistakes, we often look slower on video than we feel like we are moving. And sloppier. Don't let that get you down though. Most everybody feels this way so instead think of it as constructive criticism. How can you get better? Maybe try to improve your speed and mechanics. Then film yourself again later and compare the two. You might still feel like you were moving faster than the video shows but at least you see that you were moving faster than you were in the first video.
If you do these 8 things and put in the work, no matter who you are, you WILL get better at boxing and your fitness will improve. I guarantee it. There is no way it won't work. How much better you get may depend a little bit on other factors but you will improve. You just have to do it. And relatively speaking, they are not that hard to do. Think about this way, you've already done the hardest part. If have made the time and you are already in the gym training, that is by far the biggest hurdle for the vast majority of people. Showing up. Might as well make the most of your time while you're there, right?