All in all, lessons learned, I'd learn to be patient and think twice before passing my judgements, what was your experience and are you taking any step to redeem the good ol times?
We all have some regrets, but we can do nothing about it. What's gone is gone, but as you said, we should learn from our past and should make full use of any opportunities that we get. However, the problem is that we don't realize which good opportunities are available when they are in front of us, and we only understand them when time has passed. Do you think someone wouldn't buy Bitcoin at $1 or even $200 if they knew it would reach $95,000 one day? People would sell everything they have to buy, but the thing is, you can't know the future, so you barely take the risk.
I remember selling around 0.5 BTC for less than $500 in the past. How much do you think I regret not holding that amount? I could get $47,000 for that right now, but I needed funds, and I never thought Bitcoin would go this high some day, so I sold them. So, the point is, whatever happens in the past stays in the past; there is no point in regretting it.