You might want to read about Flow—there’s a book by that title t he at introduced that concept. The idea is this—an activity that is engrossing, requires some concentration and is somewhat challenging but is not excessively difficult or stressful—that’s a flow activity.

These activities make time disappear and can make you happy. Learning things like piano or a language can be a flow activity. Creating art can be a flow activity. Even reading can be a flow activity.

https://positivepsychology.com/mihaly-csikszentmihalyi-father-of-flow/