All I can write (lyrically) are breakup songs... they sound really great, but I can't exactly have an entire album of me singing "WHY DID YOU LEAVE ME WHY WHY?!?!?" lol... you get the point. How can I learn to start writing about things other than failed relationships?
Write about anything. Write about absolutely nothing. Write about the orange you ate for breakfast, about feeding your dog, about an interesting conversation you had with your brother. Just write about something other than what you don't want to write about, anything. Make it something that only you can tell me about, something unique that only you have experienced the way you have experienced it.

You'll find that your writing will be much more interesting than when you were writing about breakups.
Today I feel electric grey
I hope tomorrow, neon black
bump thanks for suggestion any more suggestions are greatly appreciated =)
Two of my favorites:

Pull a story out of the newspaper and use your imagination to write a song about it.
Pick three non-related powerful images and try to connect them with your song. It's guaranteed not to be cliche (like every breakup song ever), and it gets you thinking about how the form of your song can be used to control and shape ideas rather than just cramming ideas into the empty container or a song.