If you need the money or cannot cope with losses, taking some profits is a good idea.

What is "some"? That depends on the individual.

It becomes an issue when you withdraw the vast majority (or all) of your BTC holdings and don't re-enter the market.

I'll never forget this 20-something guy who bought ETH at $10 and sold it at $6 because he said he needed the money.

Don't be that guy.