The level which means you keep doing it is the right level. For me that's 20 minutes a day on a rowing machine plus some body weight strength exercises. Which

The level which means you keep doing it is the right level. For me that's 20 minutes a day on a rowing machine plus some body weight strength exercises. Which is about a YouTube video long and as a result I basically only watch YouTube content when I'm doing it (hey I'd like to watch this -> I should go start rowing) is a surprisingly good motivator.