First and foremost, when the time comes take some fucking profits.
This is what I must regret.
If I had take 10-20% profil I would had recover almost all my investment and would be relaxed now. Possible buying more.
Never try that. Never sell until and unless they're worth enough to make you rich. That's what I've learned from an epic bull run of 2017. I was almost 90% out of crypto by August-November 2017 because I "took profits at 1.5x to 2x".
Maximize your greed, if you're ready to spend a few years in waiting.
Simple solution. Take, say, 10% of your "new" profit on the way up.
Say you have 1000 as a baseline, you go up to 2000, you take out (2000-1000)*0.1 = 100.
Now you go from 1900 to 3900, and take out (3900-1900)*0.1 = 200.
In total you've taken out 300, which is 30% of your base value, but you still have 3700 left, which is 2700 over your baseline, or a total of 370%.
Suppose you now drop 86% and you find yourself at 518, had you not taken anything out you would be at 560, so the difference is 42.
You lost 42, but gained 300, hence a profit of 258.
You can adjust the 10% based on your own preferences, but this way you won't ever go 90% out of crypto, while still cushioning the fall to a point where you will either be happy with your profits spent on random toys, or have cash ready for the reversal.
tl;dr Take out a fixed proportion of your profits and don't worry about being "all out" or "all in" ever again. If you want to get fancy you can use variable rates, but you better double check what you're doing before you start.