Focus!?

I have all these story ideas in my head, mostly just taking up space and gathering dust unfortunately. I try to get them written down, but by the time I start to actually do so, my mind has wandered off to the next great story idea. I just can't stay focused on a story long enough to actually really write it. I even made a long list where I have written down the gist of most of these story ideas, though many are still not even in that list, but the actual writing of a story never really happens. With the only story I have started posting here, "The world through grains of sand.", I ended up getting "distracted" by other story ideas and other other real life things. With the end result that I've only written 4 and a half chapters of it.

Anyone got any good advice for me or how they go about tackling this problem? I bet I'm not the only one with this problem. A flighty muse you could call it. Or just a general problem with staying focussed. At the moment there are actually 2 stories that I really want to write, but I can't choose. With the end result that I don't write anything at all and try to find new stories to read instead of writing anything myself.

So, what do you do to beat your muse into submission?

Cheers,

Angarato