loosen up

verb

Etymology: Compare Old Norse leysa upp (“loosen up”).

1. To become loose; to loosen; to relax (a muscle, etc.).
2. To relax; to act less seriously.

   “Michael in turn benefits from Tom. He loosens up a bit, stops talking so much like one of the bad novels he used to read, and learns to give his intellect a rest once in a while in deference to the emotions.”