"Listen to your body."
We say that a lot. We want you to push yourself, but we don't want injuries, we don't want puke, we don't want blackouts or ambulances or any of that. And if you're elbow is screaming at you while you do push-ups, or your shoulder is clunking and grinding when you do presses, that's your body begging you to stop. And if you don't listen to it, you can bet you're in for trouble.
However, your brain is a dirty liar. It will tell you that it's too hard, that you're too weak, that you can't go any farther, that you need to rest, need to breathe, need to set the bar down. But 99 times out of 100, it's lying to you.
Because here's the secret:
Your mind will quit a thousand times before your body ever does. Learn to see your body for how strong it really is, learn to filter through the lies you tell yourself, learn to trust the phenomenal physical strength that you have within you and there's no end to what you can do.