1. Forgive yourself. You aren’t perfect. No one is. Recognise that beating yourself up will only make things worse. Instead, forgive yourself, and then decide to just move on.
2. Focus on motivation. Without motivation, you can’t do anything. It’s much more powerful than self-discipline. So when things get tough, remind yourself of why life will be better if you reach your goal.
3. Make it easy. Discipline is tough so remove some obstacles. For example, if you’re having a hard time exercising, make it super easy by just doing 5 minutes to start with. If you can make that change for 30 days in a row, you’ll have developed a new habit.
4. Focus on enjoyment. It’s hard to push yourself — and to have self-discipline — when you hate doing something, or you see it as a drag. So do whatever you can to create a sense of fun. For example, if you don’t like exercise, find some good music, or a workout partner, and focus on that part of the activity.
5. Repeat. You’ll almost inevitably slip up from time to time, no matter how good, and committed, you are. Just get up, get going, and keeping marching straight ahead.
Source: http://zenhabits.net/6-small-things-you-can-do-when-you-lack-discipline/ (Adapted)