If It Ain't Broke...
The old adage usually implies staying the course because doing something risks disrupting the status quo. It further assumes that the status quo is preferable to alternatives.
Just because something isn't broke doesn't mean it doesn't need breaking (triple negative FTW!). Settling for average can be more detrimental than aiming high and failing.
So, find something in your life that ain't broke—maybe a diet, exercise routine, or bad habit—and break it.