Mine is different it's not about buying the right coin, but not selling the right coin at its all-time high, I have a good number of Kucoin and it hit an all-time high of $15 I bought Kucoin when it was only at $1 level that could be the best time to sell, but I control my self and tell myself that it could go $50 in a short period of time.
That's the worst decision I take one week vacation in a place where there is no internet, hoping that when I came back it will be worth $50 but tyo my surprise it went down to $2, I should have sold some when it hit $15.
It is why I have my personal approach like that:
After identifying good coins that I have big interests in, and buy it for my portfolio; I will set up my sell orders for at least 50% of those bought coins.
This way, I will not have to struggle with my own feelings and emotions when price takes off, then I don't know which price to sell. People has basic greedy instinct, so without detailed plans to take profits, we usually hesitate when price hit peaks, and over-expect that it can move much higher. I learned this lesson from altcoin amazing year in 2017; then I changed my profit-taking strategy entirely.