to be honest, we all don't know the right time to buy coins even though the conditions where the exchange is red, so when you buy coins it can still potentially collapse, so in my opinion when you buy a coin then you should be able to hold it until the price is green and sell it more expensive when you buy.
The higher the price of a coin, the more difficult it is to make a decision to buy it, because despite the fact that we see a bull market, a high price may indicate that it may change to a bear market. But in the event that the price of a coin begins to decline, it is better to sell it than to hold it for several years until the price recovers.
Yeah, is a tough decision, and that we mostly put in luck if the market will spike high, not a dump trend to come out after buying. That is why I'd never take the risk this time with Bitcoin but have to choose potential altcoins that aren't yet in hypes coz I was thinking that altcoin season will come next to Bitcoin. I saw this happening last 2017 and I have the faith to make it happen once again this time, but of course, it needs patient.