I've been painting in watercolor for a long time and still marvel at the personality of the medium.  My latest experimentation has been to try and understand contrast, and more specifically working to get the darks dark while still maintaining the flavor and texture of the medium.  I like to give myself "problems" to solve which hopefully reflect ordinary subjects with an unpredictable "twist" in my work.  Some succeed, others don't, but it keeps me challenged and learning.