It’s not always going to be fun.
It’s what makes you a professional rather than a hobbyist.
Because you’re in it for more than just fun. If you’re going to have a set of problems, these are the problems you’ve chosen. It’s going to be hard. It isn’t always going to be fun. But the work that you’ve chosen will continue to be there. Ready for you to take another step forward.
If a hobby stops being fun, you should get a new hobby.
If your work isn’t fun for an hour or a day or a season, no need to worry. Keep going.
