I remember of a friend who gave up his studies and went all-in on AMP coin (Synereo - if you remember the project). By saying all-in, I don't mean that he invested any money on it but all his time. He worked as a programmer for them and used to earn $300 worth of AMP each month. He did this for at least 3 years, the project did well and he almost became a double millionaire when the spike occurred in markets during 2017 when BTC was $14k and reached $20k. But he kept the coins as it is, didn't sell them when I even advised him to do so and later when the crash happened, the project itself came to an end putting all his work and savings under the grave. So, you need to know when to sell as that's too an important part of trading.
Sad, that was a hard earn money if he only knows when to sell or just convert it to bitcoin and all will do good even if one can't get to the bull run or the ATH because there will be always a good time for bullish bitcoin and it may happen again in a short time or not depending on the market. However, All I know now that market is good and advise to all who hold altcoin is to sell it so it can be a good asset if converted correctly may it be fiat or bitcoin.