(idiomatic) To relax and enjoy oneself without restraint. / (idiomatic) To cease to care about one's appearance, allowing oneself to become unkempt, overweight, etc.

To belittle oneself in judgment; to underestimate oneself and one's abilities (and thus avoid being acknowledged to the deserved extent).

(idiomatic) To become successful on one's own initiative.

(idiomatic) To make oneself comfortable as if one were in one's own home.

(idiomatic) To thrive or succeed.

(idiomatic) To create a predicament or problem for oneself; to do something that leaves one with no good alternatives or solutions.

(idiomatic) To focus excessively on one's plans or on prospective future events without paying adequate attention to the present.

To calm down; to stop behaving in an erratic way.

(idiomatic) To eat to excess; to overeat; to gorge.

(UK, informal) To consider one's attitudes or behaviour with a view to reform.