Ohh this is very interesting to hear! It felt like that the last halving happened just a few months ago. I remembered checking all of my BTCs and their value skyrocketed since I HODLed most of them. Fortunately and unfortunately, after the halving I cashed out majority of my BTCs and that taught me a valuable lesson to invest long-term and take advantage of its value.
The good thing about halving is that it takes a considerable amount of time for all of the supply of BTC to be circulated. Every halving means that the BTC in circulation would be cut down as its denominations would considerably decrease.
Cashing out in plus is not unfortunate. Sure, now you know that you could have made more money if you didn't cash out. But you couldn't have known that the price will go up. It could have went down and then you would be happy that you cashed out. The only unfortunate thing is if you need to cash out while you are losing.