Trade too much - You don't have to enter a trade everyday even if you're a day trader.
This will create a kind of poor mind set that can expose traders to high risk.
Trade randomly - Don't trade every coin. Be smart, choose coins you're comfortable with. Don't gamble, always have a plan and follow through on it.
Trading better coins will be best, number one of them is bitcoin. Some coins are just not good while may coins are shit coins, shitcoins that people will trade but keep losing.
No stop loss: This happened to me once. I lost a chunk of my capital. Stop loss was created for a purpose use it for every one of your trade.
This depends, and also depending on the analyses. If it is spot trading, there are may times there will be correction, and after the correction is bullrun again. Stop loss can help but it has its own downside too.