It's all down to Persistence, baby. Psychotic Persistence no less. Jay says, in with characteristic clarity and eloquence, that all the successful authors he knows share a single trait:

What they have in common is psychotic persistence. Almost all successful writers exhibit behaviors which would be unhealthy perseveration in the everyday world, but are critical success factors in publishing.

Well said, as usual on Jay Lake's blog. Sadly, I have yet to exhibit this trait.

While I have the persistent feeling that I should be writing, I'm still in the "learning/thinking" phase of things, studying how writers I like go about constructing their stories, picking up bits and pieces of story ideas and collecting those. I guess it is a step in the right direction, but something still holds me back from just writing.

I think it's fear of failure. Stupid really.