You can cheat a little bit when lifting. If you feel your targeted muscle groups getting fatigued, then put some body behind the last few reps. You don't want to cheat a lot, though. Stay in control of the speed of your repetitions. Keep in mind that if you compromise your form, you will run the risk of injury.
Drink a little milk before you go to bed. The small boost of calories will prevent your body from turning to muscle for energy while you sleep, which will slow down your progress of building larger muscles. Have your milk with a bit of cereal, or try yogurt or cottage cheese with fruit.