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.
Many similar stories happened back to 2017/2018 during the ICO boom. Almost the majority of users focused on storing new altcoins and just use bitcoin to make a cash out. Honestly, i was one of them when i participated in bounty campaigns and have a great portofolio of alts but didn't think for a moment that it's a bubble. After a short period of few months, all the alts in my portofolio dropped to zero and i didn't make any profit from what i was thinking. It was the hard lesson for me to know that Bitcoin is the safest investment and the majority of alts are bullshits that no one can rely on.