Practising the skills related to your job is always a good idea. You can never get enough practice. However, designer and author Steve Gordon Jr suggests also focusing on skills that are unrelated to your core competencies to help boost creativity.
In the book 100 Habits of Successful Freelance Designers, Gordon (no relation) suggests that you need to look outside your typical skill set and learn new things in order to keep your brain fresh.
But to really give your creativity a boost, go take a class in something that isn't design related. Take a creative writing class -- you'll learn a lot about how to organise ideas and tell a story, skills that will help your present your work… How about drawing or painting? Pottery or knitting? Almost every town has a local arts center that offers several-week sessions of community classes in the evenings. Find yourself a creative outlet that has nothing to do with design and your designs -- not to mention, your state of mind -- will certainly improve.
Even when it seems like a skill is unrelated to your work, exercising your brain helps keep it flexible. As we've talked about before, your brain is a changeable organ. Reaching beyond your comfort zone helps make new connections that can help your work in unexpected ways.