No Expectations

A lot of times, people don't want to write because they are afraid they will make something they will regret.  But there's a funny little trick about regret (or any other form of disappointment): you can only be disappointed if you have expectations.

If you expect to make something brilliant and perfect, you will always fall short.  If you expect to write something terrible, you will always meet or exceed those expectations, but then you are never shooting for the stars.  The trick is to expect neither the best nor the worst; expect nothing at all.

Start writing with no expectations.  Just keep going, without a care in the world.  When you finish, you will have something you can judge as worth pursuing or not.  This is another one of those cases where the hardest thing to do is to start writing, so finding any means to put pencil to paper will help you instantly.  This is also another case of learning to separate yourself emotionally from your writing.  If every single idea you had became a crusade for you to see through to the very end, you will get not a lot done (and you will probably put a lot of effort into a so-so story that could have been put into a much better one).