The 3 things you shouldn't do in trading in my own opinion are

1. Don't trade if you don't know what you are into - Be informative on the latest happenings in the market especially if you aiming to buy some alts there a good research is needed so that you will not fall on dead or been trapped on dumped coins.

2. Never listen to the fuds sometimes there are sick people who spread fud news just to create panic to the newbie traders and if you been caught by them for sure you will miss the gold(profit) times or worse you lose your money.

3. Hand your money to the people who said they will trade for you and you will earned a percentage daily since a huge possibilities that they are 100% scam.