reverse course

crash course

A quick, intense course of learning, especially one which is informal or hurried.

due course

Regular or appropriate passage or occurrence

let nature take its course

To permit events to proceed or a situation to develop without intervention or interference.

matter of course

A natural or logical outcome; perforce.

par for the course

To be expected; normal; common.

stay the course

To persist or continue, especially in the face of difficulties.