Have you ever stopped to think about what you really love, when it comes to writing? It's a useful thing to do, if only because it reminds you that there are things you love about it. Everyone needs reminding of that sometimes (in my case when I'm trying to do four or five things at once, and it starts to feel a little more like work than I ever intended. Though it is work, obviously).
So what is it I love? People go on about the moment of publication, or getting a great review, or getting sales, but those are all down to other people. What I really love is that moment of working something out. Of solving a problem in the detail somewhere that would otherwise make things bumpy. Take just now, when I came up with a solution that allowed me to get in the moment I wanted in my current WIP where the hero finds that he wasn't actually as responsible for an early moment of success as he thought he was. I needed a way to get to that, and to have him making something of that success at the same time. It's such a tiny thing, but those are the moments in writing that feel good, because they're not about craft, or typing away, or anything like that. They're just me and my imagination.