To sustain exercise is the most difficult but also the most important part of a weight loss program. To stay motivated you can try following tips:
1)Get a partner, a friend, spouse,etc.
2)Make your exercise a fun! Enjoy it.
3)Have variations in exercise pattern. Try Zumba, Pilates, Aerobics, Yoga.
4)Set small,realistic and achievable goals.
5)Reward yourself with healthy snack or a little gift on achieving small goals.
6)Train early if possible, evenings become dull.
All the best for your weight loss program. Hope the tips help you.