It's all about love. 
The stories I work on are stories I want to see finished to the end. Of course, I do want other people to see them because story-telling is just in my blood.
I'm confident that not everyone will like my work.
But I'm also confident that I will like it, and I guess in the end, that matters more to me.
So what kinda drives me to get working on the script and the pages is my own love for the story. I want to see those stories come to life, and I personally wanna read them once they're finished. For me, as long as I am my biggest fan, I can keep working on my stories and improve them as I go along.
I can definitely see why it can be hard, especially if you go into comics with also the purpose of finding an audience. It's downright scary sometimes because hey -- most of us know not everyone will love our stories as much as we do. Sometimes, people will tear into your stories like sharks.
I guess my way of seeing it is that love has to be your confidence. It's not always about how well you drew the panels or how perfect the writing is. All of that can be improved with time and effort.
Sometimes, it's more or less the case of "do I love this story enough to follow through?"
If the answer is yes -- you got it made 
Even if you are your biggest fan, that's still a fan in my book. And that's what can get a story finished. 