You're not always in control of whether your job is fulfilling. Maybe you've been lucky so far, but it's unlikely to last forever.
A piece of advice: The moment it stops being fulfilling for you, you may get the urge to change jobs to something that you think will make you happier. You may change jobs several times trying to rediscover that initial feeling that made you satisfied with your work. But it may never come back. And if it's anything like my situation, in the end, the first job you left may have been the best of the bunch, and you come to the realization that the original satisfaction you had was a fluke and you may never find it again.
There's two ways you could go about fixing this. One is to keep job hopping until you get something that was as good as the first job. The other is to accept that it's just a job, and to try and not derive too much of your happiness purely from work. (Or, more generally, try to not derive too much of your happiness from anything you can't control.)
I think it's important to figure out why you found some piece of work fulfilling. I think a lot of people don't have a good understanding of why they like doing the things they do.
I know a lot of people who say, "I do this job that I hate, and I have this other hobby that I truly love, but if I were to make my hobby my job, I think I'd learn to hate my hobby." I used to say it about a number of things. I love to cook, or I love to paint, or whatever, but I work as a programmer because it's what I can stand to do for work.
And then one day I had gotten so sick of working for terrible companies that I thought I couldn't be a programmer anymore. Then I spent about a year kicking around a bunch of bullshit ideas, trying to find work that wasn't programming, that was "more fulfilling". And ultimately ended up doing a lot of programming in that time, because I had falsely concluded that my terrible work experiences were just "the nature" of working as a programmer.
I didn't hate programming. I hated working for consulting companies ran by MBAs. What I eventually realized was that I love programming. If I had been a graphic designer in those same situations, it would have made life even worse. Programming itself was the thing that I was enjoying that mollified my discontent with my employment situation. Any other job would not have been as satisfying as programming, which is where the concept that I'd "learn to hate" photography or music or teaching or whatever.
Some people I know do the work because they love solving problems for their users. Some people do it because they love learning new things all the time. But I don't think they really know that about themselves. I think they have a surface understanding that, somewhere around this area of this job that I'm doing, there is something here that I like. But they don't have their thumb on what part, exactly, that they like.
I think it's very important to pin it down because I also think it's very important to be able to recognize if it is no longer the thing you love. It's perfectly valid to change your mind about what you love. You might start out on your career loving the intellectual challenge of programming, and you might learn over time that you love interfacing with users even more. But if you haven't taken the time to deeply introspect on what particular aspect of the work it is that you are enjoying, you'll lump it all together as "I love software development", and then wonder why things have gotten bad when you're still a software developer but are now working on database schemas rather than requirements gathering.
You can't know how to fix a thing if you don't know how it's broken. And you can't know it's broken if you don't know what it should look like when its fixed.
A man cannot step into the same river twice, for it is not the same river, and he is not the same man.
The circumstances that made the first job great were no longer there even before I left it, and the role doesn't even exist any more at this point. I've looked at joining (roughly) the same team again but the responsibilities have changed so much that I can't really recreate the same magic.
Live close to work or remote. This reduces commute times and frees up time during your day. Take vacations and do things that excite you. If not remote, take advantage of days you can work from home and go for a long weekend somewhere. Or work from home for a week and go somewhere.
Work to live not the other way around. Clock out and do things.
I'm not sure that's quite the scenario the parent posited. But there is something of a middle ground where you don't necessarily love/are energized by every hour of every working day but you like it well enough on net and you have the flexibility and financial freedom to do things outside of or adjacent to your day to day job that you want to do.
