Well you never want to be too loose or too tense during a fight. Boxing, like life is all about balance.
Find your happy middle ground of being loose and being tense and you have to focus to train your body to do that as well.
Explosive power and stamina are very hard to attain but things you hate working on in the gym are usually the most beneficial for you in a fight so you have to take pleasure in your pain during training knowing full well the guy you're going to be fighting is going to feel much worse than you do when you're training.
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