This is probably the best advice.

My therapist helped me first acknowledge that it would be a long process to overcome procrastination and to stop being too harsh on myself. Then, I tried to do the smallest possible step that I was capable of doing towards the task I was procrastinating on. This could be as tiny as just sitting at my desk for a few seconds. The next day I would sit for a little longer. Then I would just open the file I was supposed to work on, etc. That's where the therapist was very helpful to me, she helped me overcome the guilt of doing something so ridiculously insignificant and be satisfied with it, while at the same time treating the deeper roots of the problem.