Consider this post a double-tip, because what I'm about to tell you will not only improve your writing, it will get you writing and keep you writing. But be forewarned, this isn't a tip for the timid! You'll need some creative backbone to follow along.
Here's the tip. Write about something that makes you angry. Thunderously angry. Something that makes you want to explode with emotion and opinions, something that pushes every button you've got and threatens to overload you.
The reason you need to do this is because, simply put, this is where some of your best writing is waiting to happen. That's why you're broiling with emotion, because the anger inside of you is also a flare gun signaling: "There's poetry here!"
Don't believe me? Try reading Plath's "Daddy," Ginsberg's "Howl," Shakespeare's Hamlet, or crank up some classic rap, metal, or blues. Anger is as much a part of artistic expression as love or beauty and often, it's best when they're all mingled together.
Here's a simple test. If I asked you to write 500 words on a politician you most admire, it'll probably take you longer to come up with something than if I ask you to do 500 words on the politician who most ticks you off. It's much harder to write from a perspective of adulation than it is from anger.
There's really no limit, either. You can go to Spinal Tap 11 with your anger and it won't hurt anything. You can murder's, mangle, shred, explode, and crucify your enemies. You can ridicule them with language, you can imagine them shredded in a chipper. Or even better you can somehow turn them into lovers and friends.
Just remember: art is catharsis and healing, but it's also a refuge. So don't spill enough imagined blood (or tears) to ruin your sanctuary or scare or gross out others from visiting and sharing your stories.
I'm not saying you should always write from anger; I'm not saying you should write from anger most of the time. I'm simply saying: don't be afraid to write from an angry place because it's often a source of incredible poetry and it will help you let go of emotions that might be weighing you down if not for the poems you write.