If you have been in a bad accident or have an addiction problem, you may go away for a stretch of time to rehabilitate yourself or, in other words, bring yourself back to health.
Though we hear a lot about rehabilitation or "rehab" in the press in connection with drugs or alcohol, the word rehabilitate has a lot of other meanings. You can rehabilitate a building's structure by reinforcing it with steel beams, or rehabilitate your bad reputation by staying after school to help clean up the grounds.