Exercise your writing muscles every day. Just as you should exercise your body regularly by walking, swimming, gardening, or your favorite activity, you should keep up your writing fitness by putting together words of some sort every day.
It can be in your special niche or unrelated. Nothing is totally unrelated, but variety can feel refreshing. If you work in fiction, do an occasional poem or song lyric or essay. Think of it as cross-training for a writer.