You should always train within your physical and mental limits, rather than pushing yourself to the edge an beyond. Give your body a chance to do what it's capable of doing. You can only push it so hard and grow so fast. As I've said before, no single workout or training session can solve all your problems as far as your lifetime fitness goals are concerned. No two weeks or even two months of training will solve all your problems wither.
Consistency is what counts.
It's continually stressing the body over time that produces a champion. Nobody ever became a champion as a result of one workout. Or 10 workouts, or even 50 workouts. It takes years of training. And the training doesn't have to be drudgery or hell on earth.