Just look at the attitude of the person who bought the pizza to answer your question. Money in the crypto market is uncertain because you can suddenly become rich or poor from your investment only you should not feel the loss. I bought a lot of other coins a few years ago including bitcoin which would have made me rich now but i sold them at small profit. Actually it is better not to follow the past time of life and we should make a big dividend in future. However bitcoin may be $100k in the future so buy at the right time. We should be more active and always take risk with crypto because risk can give you big profits.
That guy who bought pizza at that time never thought that the price of Bitcoin would go like this. If we are able to ask that person again, he probably in regrets of spending that amount. For me, it was not a mistake to spend or sell our Bitcoin in the past, it is just about to happen because that is meant to be. It was not regretful because we still make a profit it unless we just throw it away. We sell them for some reasons and besides, holding it forever doesn't help the market to grow.