Have Fun, Just Not Until You Don’t
All things in moderation, including moderation - Aristotle When you have everything in excess, it's fun. Until it's not.
In economics there is a concept called Diminishing Marginal Utility: it means when you consume something, the satisfaction you get from a good decrease withbeach additional unit consumed. Or in simple words, the first bite is always the tastiest, and the more you consume the less you'll actually enjoy it.
This is true of all things in life more often than not. The first plate of food is always tastier than the second, and keep eating and you'll feel more tired than energised(which is what food was meant for). The same with watching a movie, or scrolling on your phone. Anything you consume, it just becomes less fun after a while.
The only exception to this I can imagine are experiences. For experiences, there is no diminishing utility. Each experience provide novelty. Going for a bike ride, a trip with your friends, even that become less fun if you keep doing it all the time.
Then what's the solution? Yep. Moderation. As cliche as it is, there is wisdom in these age old sayings. They persist because they are true.
Life becomes fun when you learn to moderate yourself. Food is enjoyable when you eat them in moderation. Your phone is not a burden if you use it in moderation. Even good things like exercise is best when done in moderation. Everything in moderation, including moderation.