You are not alone. I have heard similar stories from others. They sold their BTC too early. I also have a story of 7 years of cryptocurrency. I have used BTC as a payment method a lot of the time and I caught some BTC, which was earned from buying / selling digital products. However, I spent BTC at that time. I could have made a lot of money if I had kept BTC.
If you've been in the space for as long as you say you have then it's quite weird to hear you say you've used it and look back and say you should have kept it.
Newbies tend to say it but we all know that if we don't use it and everyone just holds, BTC would never go up in value. You've been through 2 past rallies and now in third. Surely not the time for regret?
I think whatever changes on the value of BTC, there is always a regret and we mostly rant about it. When it is down, you regret not to sell when it has higher value but never try to buy some when it happened, then you gonna regret again when the price got higher but you dont not have any investment from it.
Every situation is an opportunity rather than regretting it, take it. Buy when you have to hold, then sell when you think you already have profit. Take risk, play the market.