Never invest what you can't afford to lose meaning if losing it will reduce your quality of life do not invest that much invest less.

Do not take out loads you might not be able to pay back if things go wrong this means not only do you lose money on the investment but you are now paying interest on a loan you can't afford to pay back anytime soon, you will become desperate and we do silly things when we are desperate.

Strike when the iron is hot. If the value of your coin has grown to the point where the return in a large amount does not keep holding in case it crashes. Sell as many coins as you can in order to pay yourself what you feel you deserve and then hold onto the rest. Meaning gets your ROI and a small profit at least.

Never sell too early especially during dumps, if it is a coin you believe in this is the time to buy not sell.

Never trade while hungry/thirst/ under emotion strain or distress /tired/ drunk / high / etc. You need a level head when you trade. Rather sleep if you are tired. You might lose out on a good deal but what if you so tired you make a huge and costly error? Better to be of sound mind at the time of trading.

Always withdraw your coins from your exchange account asap. An exchange is not a wallet it is not there to protect or store your coins it is there to trade. It is a market. Withdraw when you re done.

Set up a pin code when trading that is asked before each trade. This prevents mistakes.

Other than that there are the other things the others have already been mentioned. These are just some of my personal ideas.