Generally I avoid this by trying to focus big picture stuff. Say I make a 8 bar loop bar loop like this:
https://dl.dropboxusercontent.com/u/765 ... /loop1.mp3I would then go farther into the project, and just make a new loop using the same resources with a new sort of groove, a different feel like:
https://dl.dropboxusercontent.com/u/765 ... /loop2.mp3Like, not so that I know the first loop has to fit with the next, just so I have more, to spawn more ideas. Its sorta like I'm making A first, then C, to make it easier to figure out what B is. Trying to work non-lineary really helps me when I'm stuck. Like its different for what music you make, but if you're making house music and you're stuck on the verse, just start making the drop. its a lot easier to interpolate than extrapolate, if you get what I mean.
Another thing I do in my mind is that after a loop you have three options: Repeat, variate or make something complettely different. Decide on which you think is best for the moment. Like if your verse is only 8 bars, you can easily repeat it another time and make it 16. If that gets too repetive, variate it. If you want a new part, like a contrast, you probably want to make something new.
Sorry for makin sort of a rambling post, but this is what I do anyways.