There's nothing to regret. A lot of people bought Bitcoins in December last year. I know a few friends who bought a lot of altcoins at this time and have lost more than 90%. If you stick to your investments, I don't think you're going to lose much because Bitcoins never happen. It will disappoint us.
Yes, there is nothing to regret as huge investors bought at $20k rate, they are holding and try to buy now for profits plan.