The great old-time banjo player Wade Ward once referred to changing the tuning on a banjo as changing the “atmosphere” of the instrument. By this, he meant the entire feel of what you can play is shifted by the tuning. This sentiment holds true for the guitar as well, because a simple tuning change can greatly vary the feel of what you play, while at the same time helping you to discover new arrangements (and to avoid ruts in what you play).