Taking care of yourself as a designer or just in general is important. For one as designers we sit down all day staring at a computer screen. Well that may be different for some more then others. I started doing insanity a couple months ago and I am glad I did.
Because realizing that the more you sit down, the worse you end up feeling. That may not be the case for you. Another thing was wanting to feel better. By feeling better I would work better and therefore produce better work. When you first start taking better care of yourself then you want to do the same thing in other aspects of your life.
To keep this short start doing whether its yoga,taking a walk around the walk or even going for a bike ride. Getting outside will do nothing but have a positive effect on you. Remember how you were as a child when you loved going outside to play? well its time to bring that back again and enjoy nature instead of being inside all day. Remember that healthy body and mind leads to a healthy life.