Why do you always "buy and then it drops, sell and it rises"?

It's not because you're unlucky, but because you haven't made enough trades.
In futures trading, there's a concept called the Law of Large Numbers:
After you complete 100 trades, your win rate will infinitely approach your true skill level;
When you only make 10 trades, everything is just random fluctuation.
So, true traders don't focus on the profit or loss of a single trade, but on the net value curve after 100 trades.