I've only set one for myself and it was going back for Thanksgiving last year. I wanted to be in the 130s, even if it was at the top end, and it was totally realistic, so I was pretty sure I could achieve it. I did achieve it, but even if I hadn't I would have been very close and looked so much better then when I started.
I haven't set any since then, as I'm closing in on my goal, and I know that my losses will likely creep along for a good few months and I'm fine with that.