I love the act of writing itself. I suspect that I have the same feeling that someone who loves painting or cooking or gardening or dancing has while doing those activities. While writing, I am engaged, excited, stimulated, challenged, curious, hopeful. Writing is a form of communication, and it feels very human to try to communicate with a reader through words.
I write for the pleasure of solving a problem, realizing a truth, understanding another I write to make something, to feel something, to live something.