I recently watched a tournament at PokerStars with a prize Pool of $ 10,000,000. There I saw several familiar nicknames that have been playing poker for more than 8 years. They are able to earn good money on poker. However, as you said, this income depends very much on your ability to remain calm. But not everyone can do this for many years. Gradually, the ability to remain calm is lost and a person wants to relax.
This is very similar to what happens with day trading, the few day traders that are capable of becoming profitable with the activity leave it after a few years, which may seem odd, after all why leave behind an activity that is making you so much money from the comfort of your own home? And what happens is that people burn out, they get tired of watching the markets every single day and to react in a perfect way every single time.
Some leave trading completely and change their profession to something more exciting while some others still trade but become long term traders as it is way easier to monitor the markets when you only do it once at the end of the day.
It all depends on the person and their patience. Also, whether the person likes this activity or does it only for the purpose of earning money.
I have a friend who has been trading on the stock exchanges for a very long time. He started with the stock and currency markets, and now he is quite successful in day trading on the crypto market. He's always busy. It is extremely difficult to distract him and invite him to socialize and celebrate a holiday.
Personally, I could not spend so much time looking at the monitors with exchanges charts.