This is a difficult one for most people! When you keep putting something off that you need to accomplish, you tend to spend more time thinking about the fact that you have to do it when you could have already completed the task.
Quit making excuses and work up the willpower to do the things you hate to do. Once you do it, you'll strengthen your resolve and build momentum.
It's important to be self-disciplined, but you don't want to overdo it and burn out. Mental breaks will actually boost your productivity because your mind has a chance to reflect, rejuvenate, and repair itself subconsciously.
Schedule frequent 10-minute breaks to clear your mind.