Skills like muscles can atrophy by underuse. How you hone your skills is important to how well your career will develop overtime. It is never useful to be stagnate and to assume that what worked for you yesterday will work for you today and in the future. There is no better way to enhance your career, instill confidence in your abilities, and put yourself on the trajectory for a raise or promotion than to enhance your current skill set.
Skills can be enhanced a variety of ways including learning something new simply by doing it. As the saying goes practice makes perfect. Consider when you first learned to ride a bicycle as a child. When you first learned you may have used training wheels or where even a little wobbly, but as time went on and you no longer allowed the fear of falling to keep you from getting on the bike your once wobbly bicycling advanced to riding longer distances, turning curbs, and maybe even popping a few wheelies.
Don't let your career go stale challenge yourself to enhance your current skill set or maybe even try learning a new skill.