The first time you receive payment for your creative work is something you'll always remember. It's a special kind of validation and affirmation that you really can pursue [enter your specific creative work here].
Quickly and easily, however, the work can become more about production and less about creativity. Most full-time freelancers will hit this wall time and time again -- we both have. Here are few suggestions to keep your work fresh.
Seek a second opinion. Bring in a pair of fresh eyes. Even if you practice different mediums, it's wise to seek a second opinion from someone you trust.
Set goals for yourself whether it be learning a new technique, using a new piece of equipment or software, etc. When I was studying ceramics in college a student teacher told me it was unlikely that I could make 100 different mugs. And so I tried, and did. I'm a firm believer in quality over quantity but sometimes an assignment like this is exactly what you need to stretch your creative limits.
Learn from others, be inspired by others but please don't copy them. The thought that copying is the highest form of flattery... we don't buy it. You're a unique individual and we believe that your work wants to and needs to reflect that. When you see work that you admire, take note of soak it up but ask yourself how you can take it a step further.
Practice other mediums. Make it a point to dabble. Each element of art is influenced by the others -- but even if you don't walk away with a life-changing method to apply to your primary medium, at least you've let yourself create with no agenda. Hopefully you'll walk away refreshed and excited to continue making.
Revisit your "why." I don't think you can do this often enough. Mark off some uninterrupted time to write down what you love about [again, enter specific medium], and how it contributes to the lives of others. This manifesto of sorts may flux over months or years, but if your reason for creating remains pure (because you love it not solely because you're making loads of $$$), revisiting this statement may be the pat on the back you need.