The drive to learn, to share my progress and to know you can make people happy with what I do is what motivates me to draw, even if i'm not the best artist out there :]
I'm not the best artist by any means compared to most people here and I started sharing my stuff 5 years ago, being fully aware I had so much to learn (and I still do).
Maybe I also make garbage, will that really stop me from trying my best? nah, I love drawing and I love to learn alongside other talented people.
Do you draw well because you love to draw, or do you love to draw because you draw well?
It's easy to say that love and passion is what makes things move that way. But how many people, aware of their mediocrity, would love to create garbage?