To my considerable surprise, I posted a fic to my AO3 account this morning. Okay, it's under 700 words, but it's a whole, complete fic, written in about 20 minutes from a prompt. Looks like these things really are like riding a bike.
In case you haven't seen it, let me recommend the community
comment_fic to you. It feels like old-school LJ, with a daily theme post, the chance to leave prompts, and plenty of people leaving fills and feedback. I like that it's multi-fandom (but LOTS of SGA prompts, interestingly), and that it's low-key. I'm going to try and put something in there each day, even if it's just a few hundred words of fluff. The point is to build the habit up again, not to write Star Wars: War and Peace.
Link to fic:
In the SilenceFandom:Star Wars: The Force Awakens (includes mild spoilers for the film)
For the prompt: Star Wars, Han Solo & Poe Dameron, The man who taught him how to snark out of trouble.
Although apparently I'm in a melancholy mood at the moment, because I took the prompt in a somewhat sideways direction. Nice to know I haven't lost that habit either!