1. Mr. Jones goes to work and does the same old job every day, and he never does anything different. He’s on a treadmill
2. Everyone thinks I’m so predictable, but some day I’m going to get off the treadmill and do something adventurous.

Synonym: in a rut. Compare to: old hat. A treadmill is a machine consisting of a continuous belt or moving steps that circle around and around and to which there is no end. The expression is often used to describe one’s job or daily life.