Lol ejwriter. I was so used to writing in like AIM form that I wrote it on here (I kind of got yelled at by like 13 people when I asked a question and they all answered this question made me cry - I was like what? sorry and then I realized it was my grammar.....)
You might try writing your posts as though you're writing, not as though you're talking. I, too, say "like" more than necessary in casual conversation, but you'd never know it from my posts here. I'm not yelling, just trying to help you out so you can learn from and be encouraged by all the great people here, as I certainly have.
As for having trouble finishing, it might help if you pinpoint the problem. Is it really just that you've lost interest, or are you having trouble with the art of writing an ending (many authors do)? Can you not figure out what should happen next? I sometimes suffer from a fear of finishing. I'm plenty motivated but worry that once I'm done I'll find that it just hasn't come together as nicely as I hoped, and that it really was terrible all along.
Or are you losing interest because the story is truly no longer interesting? Is this a point where a reader would put it down, too? How can you tweak it so it gets interesting again?
If it is just losing interest, then you've got to discipline yourself to keep working at it. Eventually, your interest will be sparked again.