What drives us? The answer is different for everyone, and everyone has many answers. The desire to achieve. The desire to be heard. A need for success. A fear of failure.
I've written about writers and imposter syndrome; related to that is the fear of mediocrity. In my experience, many writers do not fear failure as much as they fear being not quite good enough. Perhaps they're good enough to keep their friends turning pages but not good enough to get published. Or maybe they're good enough to get published but not good enough to get stellar reviews.
However you define success and mediocrity, the problem (and advantage) with this line of thinking is that we're never satisfied. There's always one more milestone that we need to feel validated as writers. This can drive us to keep creating and keep working hard, but it can also lead to feelings of inadequacy—which can easily stunt our work.
To combat this, it's important to take the time to acknowledge how far we've come. Remember when you weren't sure you could finish a draft? Now you've drafted and edited your manuscript. Remember when you thought you'd be querying agents forever? Now your book is on submission with publishers. At any given point in our writing journey, we are where we dreamed we would be. Even if we forget about them, we have accomplished goals.
Writers are always living our dreams. Don't get so swept up in new dreams that you forget.
Fearing mediocrity can drive us and stop us in our tracks. So here's my compromise. Don't fear temporary mediocrity. Be comfortable being uncomfortable with where you are in your writing career. Learn to accept the parts of that fear that drive you and banish the parts that make you feel less-than. Remember how far you've come, and let the acknowledgement of success drive you just as much as any fear of staying in place.
In the comments, share with us something you've accomplished that seemed like a wild dream when you first started writing.