I do this not only for sewing but also for ....housework....chores etc that I can't get motivated to do. Especially those really "icky" jobs.
I set the timer on my watch for 10 minutes and say "I'll just do it for 10 minutes, then I can quit". Most of the time, I've gotten far enough along in the task that I just keep on going....or if it's sewing/glass work I'm starting to enjoy it, so keep on going....and if not, at least had a really productive 10 minutes and more is done than before I started!