What is your #1 cryptocurrency market rule that you will never break?

As we see many newcomers enter the market, they don't have a sense for the market like those who have had long term experience.

A lot of easy to avoid mistakes are made. People lose a ton of money.

Those who have weathered the 2018 crash have some tough skin and rigid rules they will never break in the crypto market. Tons of this insight comes from past mistakes we have all made.

A rule I've learned not to break is to never sell 100% of a crypto to buy a new one. Always save around 10% or more. If I had done this with ETH over the last 5 years my ETH bag would be substantial.

What is your #1 crypto rule that you don't ever break?

Edit: Welcome and good luck to all the newcomers the crypto community is happy to have you!