This is basically how I set goals, with the caveat that there aren't that many entirely new goals for me. For example, I know I can exercise, so there isn't really a fear of failure there, just laziness). There've been periods when I've finished a novel in months despite being in classes all day and swim team seven days a week, so I know I can write ten pages in a week–I just have to choose doing it over watching stupid videos on the Internet. I started meditating, which was an entirely new activity where I felt no confidence of success, by joining a study to provide extrinsic social motivation.