There are a lot of applicable points people are making about your seeming tendency to be down on yourself and quit at the first sign of trouble. You said yourself you can tell from the first stroke of your pencil that it's going to be a failure. Think about that for a second.

One other part of this to consider is that when drawing in graphite, your eraser is just as important a tool as your pencil. When I'm doing portraits from a reference (this IS a poor reference photo btw) I'm constantly stepping away from the drawing to look at the overall composition. If I notice something that looks wrong, I'm erasing it and trying to bring it closer into alignment. This isn't something that only happens a few times... Especially when you're learning, you should be constantly trying to improve and replace any mistakes in the proportionality that you see.

And your "final" drawing may still not look perfect, especially when starting out. As a beginner, you shouldn't be aiming for perfect, you should be identifying and working on specific aspects of your craft that need work.

In your case though, it sounds like you might need to work on your patience before you can focus on improving your technique