For me, with writing, it was two things. One was to set very 'doable' goals. 50 words a day, four days a week (I had a four day work week with my job and I did my writing on my lunch break).
The other thing I found that I had to do was to define goals in terms that evaded the notice of my critic. Example: I finally finished, with those 50 words/day, a very dodgy draft, with things like notes in parentheses "(Nora and the ladies fight about what the teacup signifies)" - for example. I wanted to revise and show the story to someone feedback, but everytime sat down to work, I froze. So I redefined my goal from "Write a version of the story that someome else can read" to "Write a version of the story where each sentence is grammatically correct and connects logically to the sentence before it and after it" With this new definition of my goal I was able to finish the draft, whereas with the first one I just planted.
The other thing I found that I had to do was to define goals in terms that evaded the notice of my critic. Example: I finally finished, with those 50 words/day, a very dodgy draft, with things like notes in parentheses "(Nora and the ladies fight about what the teacup signifies)" - for example. I wanted to revise and show the story to someone feedback, but everytime sat down to work, I froze. So I redefined my goal from "Write a version of the story that someome else can read" to "Write a version of the story where each sentence is grammatically correct and connects logically to the sentence before it and after it" With this new definition of my goal I was able to finish the draft, whereas with the first one I just planted.