One strategy that has consistently worked for me when there's something I need to do that I really don't want to face: set aside some time to work on it, and then start casually thinking about it before that time arrives while I'm doing something else. That seems to help a lot with "swapping in" the mental state for the task, and when I actually sit down to work I find I'm a lot more productive than if I have not pre-loaded my mental caches this way.