I regret I don't buy bitcoin this year I was focus on the other alts. I just realized the bitcoin is on the bullish run and now the price is going to $30k USD. It is a big improvement of bitcoin from $7k USD last year January 1 from today price. You can feel the huge changes.
Its too late to regret because due to unpredictability of the market that's why these kind of situations are quite common.
We wont know on what would happen next that's why we do commit or missed out mistakes for us not to buy when its still cheap.
Lots have doubted but there are people whom do really risk out.
No need to regret when you do sold early as long you are in greens then that what matter most.