Sooner or later every designer has creative block. It's a fact. First thing to realize is you're not alone. I've never met a designer, not one, that hasn't struggled with creativity. What is unique, however, is how to handle it.
Here is what I have found that works... Do some pro-bono work
Sometimes we don't always get those dream clients we thought we would in college. If the types of projects you are getting aren't satisfying you creatively, do some pro-bono work. Usually, non-profits, struggling artists and/or musicians need the help and you need the "fresh air". It's a win-win.
Break your daily routine
Take a day off, laugh, scream, whatever. I like to do something that uses the other side of my brain. That way the 'cerebral twins' get some equal playing time and everyone's happy.
Get out of your Aeron
Air travel is cheaper than ever. Go visit someone...somewhere. Life experience is as important in design as natural talent. Go see what people are doing in a place you normally wouldn't. Even I have been in a sorority house or two...there I said it.
Pick whose opinion matters & listen
Creative directors, account reps, clients and your mom, they all have ideas - some good some not so good. I have been victim to following some bad design advice, and it is my fault for doing so. One thing I have learned is it only takes a couple extra minutes to explain why you're right. So do it. Your creativity will thank you in the morning.