Turn in on yourself
Definition 1 of 2
Pro Tip 1/3Negative Trigger
The phrase is often used after someone experiences something unpleasant that causes them to focus inward. 
He didn't talk much at the party; it's like he turned in on himself after the argument.
Pro Tip 2/3Isolation Indicator
The phrase suggests that a person may start avoiding social interactions. 
Ever since she failed her exams, she has turned in on herself, not even joining us for lunch.
Pro Tip 3/3Emotional Undertone
It implies a deep emotional process, not just ordinary self-reflection. 
Losing his job made him turn in on himself, questioning his worth.