I have a few different motivations, which motivate me in different ways.
When it comes to finishing a particular page, I set myself a one-week deadline from start to finish. I've figured out that this is manageable for me, and since I haven't missed a deadline yet, I'm motivated to keep that momentum going.
When it comes to continuing the seemingly endless slog of the story, my motivation is ... I actually intended to start this project (or another like it) almost fifteen years ago! Eventually I couldn't put it off and 'what if' and talk myself out of it any longer, because NOT trying to make something and put it out there was doing so much damage to my mental health. So there's a fair bit of NEED behind my desire to make this comic. I'm finally feeling the relief of doing something I should've done years ago. It feels right. I don't want to go back to feeling like I'm wasting my existence anymore.
When it comes to why I continue drawing, in general? I've been drawing since I was old enough to hold a crayon. I don't think I could stop if you paid me. NOT drawing would be so, so bad for my mental health.