1. Do not remember electronic wallet password
2. Do not back up your wallet
3. Do not research new services
4. Buy and sell based on feelings
5. Leave your money in the electronic money floor
I think it is common to the user and to the person who has experience on it because we are not too young if we understand bitcoin so it is common sense that we forget to do that. You can realize your post when you experience a lot on this forum and you can ask yourself on why you do that.
Yup you are right a lot of things are here that we need to keep in our mind, one of them is bitcoin wallet private key, because it gives you confidence that your bitcoin is safe and no one can take it away, the other mistake according to me is selling in panic and not to wait for the market to be green, because they value their own feeling while feeling and emotions has no concern with bitcoin earning.