My day job. Personal projects get a little more heart, but "success" to me is usually intrinsic, not extrinsic. I'm probably a little weird when it comes to motivating factors, but not alone.
Have you considered using "will the skills I hone here help me with my side projects?" as a way to decide which job to apply for? I don't have enough data to say it's a good idea, but so far I'm liking it.
I took my current job (in communications) in order to get better at outreach, marketing, etc. for when I work for myself since that's what I was the weakest at as a freelancer. I'm also interested in tech ethics so I took a job in politics so I could become more familiar with how the sausage is made.
Now I'm looking for a swe job so I can get more experience working in teams of devs since most of the tech work I've done has been solo work.
I'll let you know how it worked out in 10 years?