Landscapes are among one the most common watercolor subjects.  They do not have to be detailed to perfection.  In fact the most effective paintings are completed within 30 minutes.  Go outside and pick a scene that inspires you.  Sketch out your work then return to your studio to paint.  Limit yourself to just a few colors and two brushes.  Remember not to be so critical of your work.  Go with what you feel and you can't go wrong.