One of the most useful tools I ever started using is an Excuse Book. Any time I come up with an excuse to not do something I know I should do, I write it down. Once it’s in black and white, I can keep track of the negativity I’m feeding myself, laugh, and then go ahead and do it anyway.
When you start seeing the excuses pile up, you realize how many crappy reasons you give yourself to not do what needs doing. Keeping track is the only way I could come to terms with how pervasive my excuse-making was, and writing them down helped me stop procrastinating (almost) immediately.