1.) Don't set the bar too low or too high. Too low leads to procrastination and too high leads to discouragement and frustration. Try to set attainable goals that are bit challenging. Also, try not to pile on the goals all at once - try focusing on just a few at a time.
2.) Stay strong! You spend a significant amount of time during the day resisting things you want, like a cookie or some time to enjoy the nice weather. After a day of this, your brain is tired. Give yourself a break and find ways to avoid some of those temptations.
3.) Don't do things to please others, do them for yourself. Internal motivation leads to greater success. Talk with a a friend or family member to help you reexamine why you're doing, whatever it may be or comprise.