When those lungs start to burn and those legs get sore, push. That’s when you get the most training. Rest for a bit and then do a little more after. This doesn’t mean to continue pushing your body as hard as you can or to continue trying jumps after your body is completely fatigued. It simply means that after you have realized that you have gotten tired, don’t stop training. Take a break then do a little more, do something else. This push will make you much stronger. You’ll go past your current limits.