Welcome to the fourm.
OK, you say you have a problem, but rather than fixing the problem you want to compensate. I mean this respectfully and as someone who has performed since the 60's.
That fact that you start off OK is the answer, you can balance in the beginning, but kind of get carried away. The fix is not things to compensate when you get too loud, but seriously to control yourself and not get too loud.
It is about being a more controlled performer, not doing things that support the bad habit and then it will never go away.
You mentioned it in your post, "practicing and becoming a better performer" is the right solution. What you describe typically is nerves, and two bad habits that nervousness can generate is getting excited and louder, and the other common one is speeding up.
Don't feed the bad habit, knowing is half the battle, work on relaxing, staying in a pocket and practice it away..............