I used to go to the gym balls to the wall and leave there limping out. I was a victim of several injuries which forced me to change how i workout. the same rule applies to sports, running, swimming, whatever.
anyway since my injuries i have had to learn to train SMART, instead of just train like a gorilla.. the ironic thing is my results have been better and i am healthier and in far better overall shape.
when you are in your 20's you can get away with being stupid, but the damage you do will effect you as you age. your disc health will be affected for example