It is hard to be that person warning of the dangers of investments, but I agree with what you are saying. I think the rule should always be to never sell off an entire asset. Maybe you wouldn't see the sky-high profits that you would have with holding, but you at least have something to show for it and something left in the market just in case.
Steemit has been influential in me getting into cryptocurrencies, but I was very skeptical at first. I'm not in anyway a professional trader, but Steemit has enabled me to get into Bitcoin and several altcoins. If it all goes to nothing tomorrow I can at least say I made something from it, and the experience has been worth it.
Do I wish that I have held onto every Bitcoin? Sure, but because the way that I have been involved, I can say that at least I still have some left. If the market continues to move with BTC rising, I think I'm going to invest more into STEEM. What do you think?