Fair enough, I've said my thing. It's your decision at the end of the day :)
You don't have a crystal ball - so you can't really foresee a bad decision. You may have an inkling that it's a bad idea, but weighing up pros and cons, you make your decision. For example, you bet your monthly salary on a horse that shares the same name as your mother-in-law. You know it's a bad idea, but something inside you is telling you that this is it - your are guaranteed to win! Of course, you lose your shirt.
Do you regret it? I suppose it depends upon your attitude. You most certainly learned a valauble lesson, but that's not regret. You may regret losing the money, but not necessarily regret the process of going to the bookie, placing your ridiculous bet and watching the race. It's possible that that's the first time you felt truly alive in years.
I've regretted choices I've made in the past. I like where I am now though. I don't think I would be at this place if I'd made those choices differently. So maybe I don't regret them now.
My biggest regret...not waiting for my soup to cool down before imbibing (or eating...whatever the hell it is you do with soup). Goods things may yet come of it. Unlikely. Tastes better hot though.