Having resumed or returned to an activity that one had previously failed, had difficulty with, or been harmed by. I've been single for three years since my divorce, but now I think it's time to get back on the horse and start dating again. I wasn't sure Mary would ever drive again after the accident, but she was back on the horse within a week.

Currently using, intoxicated by, or addicted to heroin. This is your first time on the horse? Just be sure to take it slowly, OK? You can tell Tara's back on the horse again—she's been really sick looking and out of it lately.