I used to train in boxing a few times a week. That definitely took care of my stamina problems. One time, however, I went straight to a rehearsal right after hitting the gym, and I couldn't feel my hands. They were so sore, I couldn't fully close it to make a fist. Plus, my muscles would spasm every now and then, so my fingers would pop the snare at totally weird moments. That's one of the dumbest things I ever did.
If you're going to do boxing, make sure you're punching correctly. A badly angled punch can sprain your wrist, or worse.