My biggest regret was in 2018 when everything came down crashing in the crypto market, but before then I had a chance of selling some of my coins for some good price when the market was still stable but I decided to hold.
I have a similar situation. A friend told me at the beginning of the summer - sell, it for a long time. I did not listen to him. Now I could buy the same amount of coins I have for half of that money.