It’s quite difficult to give advice without any data in front of you.
As the saying goes: what question is the answer. You can make mistakes in many aspects of trading, but judging because you wrote most likely you just don’t understand when you need to enter a trade and when to exit. For starters, I would advise you to buy a subscription to Trading View and watch what the best traders in the world listen to their analytics and look at their deals, specifically at the time of entry and exit. Learning from the example of professionals is always easier than yourself.
He is wrong cause he even try to trade and make profit in that way. People just hear that trading is profitable, buy low
and sell high, like it's some simple thing to do. After they lose money, they start to think about what they did wrong and
they ask questions like they are total beginners.
Who wish to risk and lose with trading can do that, I think that investing for long-term holding is safer and better option.
You can't make a mistake with buying Bitcoin or Ethereum for the future, why to risk them and maybe lose them.