At least once a day, I type up a comment somewhere, proofread it, think about whether I really want/need to post it, and then hit the back button. I figure that next-to-last step of asking myself whether it's really something I want out there is a good habit, and if the answer is always yes, I probably haven't thought about it enough.

I definitely do the same thing and in fact did exactly that with my original post! It's a good instinct to build up.