Inertia is resistance to change. You hate looking at people's feet and yet you stay in your job as a shoe salesman year after year. Why? Inertia.
Inertia is a physics term. Isaac Newtown discovered that a body at rest would stay at rest and a body moving through space would continue moving through space unless an external force (like friction or gravity) caused it to slow down or stop. Sometimes we need an external force to help us get going or to change direction, too, like a friend to tell us to get off the couch or to quit that job at the shoe store.