Focus, focus, focus...!

I can't seem to stay focused on one task, even trying as hard as I can. My mind will say, "Okay, hop to this task," after I have been trying to finish one task for only five minutes. Why does my mind have so much difficulty?

I am narrowing it down to a few things, one being perfectionism. Am I so afraid of perfecting everything that I can't even get the basics out? I realize this in my writing, where I can spend a long time trying to get out a first chapter's beginning sentence as opposed to just letting my thoughts flow and coming back to edit a roughdraft later.

But though I tell myself this, why is it so difficult to change these habits? Why can't I ever get out my ideas in a way that feels satisfying? Will I ever be able to finish a chapter?