The hardest part of writing is staying positive.
Not in your story. You can torture your characters, be negative and bitter and deliciously despairing – well, unless you’re in genre fiction and your editor likes fuzzy main characters – but in your daily writing life. It’s easy to fall prey to the niggling demons of self-doubt and depression when your fine prose – so much better than all that other junk out there! – doesn’t garner the interest you think it should.
Remind yourself: It’s a long haul, and those who make it to the end are those who keep trying.
It’s not always easy. In the wee hours, when you lie awake, head full of embryonic plots and characters mixed with stress and worry and self-loathing for having the insane egotism to think you could be a writer, it's hard. It’s hard when you’re standing in the checkout line at the grocery store and think “the teenage dropout who can’t make my change properly made more today than I did”. It’s hard.
But no one said anything good, or important, was easy.
You have to remember that what you’re doing has value. It is innately of value, in fact, by virtue of its nature. You are crystalizing thoughts, scenes and emotions that are utterly unique. You are adding to the sum total of human experience and knowledge.
You are writing.
That’s more important than you know.