Don't exercise on a day when you aren't feeling well, or haven't had much sleep. If you do, you'll find that your workout isn't as satisfying because you won't be able to put 100% of yourself into your routine. Take a break and return to exercise when you're feeling better.
Make exercising a game. See if you can do a couple more reps every cycle. By increasing the intensity of the workout, you will lose more weight. By making weight loss a game for yourself, you will take the pressure and stress out of losing weight. Take your exercise seriously, but don't take yourself too seriously.
Exercise when your mood is bright. When you are in a really good mood, take the time to go exercise. The better you are feeling, the more you will likely push yourself. Exercising can also help you feel better than you already do, so going when you feel good is only going to make you feel even better.