The key is to keep moving forward. A lot of times in writing we hit a wall; some call it writer's block, I call it fear.
"Will anyone like this?"
"Is it too much like that other book everyone is talking about?"
"I know nothing about this genre, why am I thinking of starting this story?"
And my personal favorite, "I have no idea what will happen after this scene!"
Fortunately, there is a cure. Be the caterpillar.
Let me explain...
A caterpillar begins life having no idea that it's going to be a beautiful butterfly one day. It just eats, and eats, and eats until it starts to make a cocoon.
What the heck is going through it's head during this nonstop feast?
Oh my, God! I'm so hungry. Like ALL the the time. What is wrong with me?
Does it worry that it doesn't have time to talk with other caterpillars. And if it did, what would they say to each other?
"I know, me too!" Munch. Munch. "And now I have this intense desire to wrap myself in thread spun from my butt. It's starting to become more important than eating."
It goes through this cycle completely loyal to its needs spurned on by natural instincts.
Until one day...
"I can't believe I slept so long. What day is it? And now I'm hungry for flower nectar. What is flower nectar? Holy shit! The ground is so far below! How can I move around. Whoa, I have wings. Check me out! I'm beautiful!"
When writers block gets in your way, be like the caterpillar and let instinct take over.
Now go write something without caring why you're doing it, but trust that one day, it will be beautiful.