Again, the point is about taking gains. If you bought bitcoin at 18k and watched it go to 60k and didn’t sell anything and now you’re looking at 18k again you’re a fool. Period.
Basically every time the prices increases by X% sell Y% of your investment and don't touch the remaining part unless it is X% higher than the previous peak at which you sold. This ensures that you're realizing gains on the way up, but still benefit if the price continues to climb. In addition what I like about that strategy is that it takes emotions out of investing: Decide once what your parameters for the strategy are and then just strictly follow it, whatever happens. It's a lot easier to stomach a 90% price decrease if you realized a sufficient amount of gains on the way up.
I can totally understand the mindset of investing some amount today but not wanting to have to care about that investment for the next X years. Especially with the high volatility of crypto currencies.
[0] A good book on the topic: https://en.wikipedia.org/wiki/A_Random_Walk_Down_Wall_Street
[1] https://holdfastwealth.com/blog/why-women-make-better-invest...
I.e what if it went to 100k after you sold at 60k, and then you buy in at say 70k?