Well adjusted
Definition 1 of 2
Pro Tip 1/3Emotional Stability
This usage often implies that someone has successfully dealt with life's challenges. 
He's very well-adjusted, handling stress with ease.
Pro Tip 2/3Social Adaptation
Refers to how effectively someone fits into social groups or handles social situations. 
Despite being new, she’s a well-adjusted member of our team.
Pro Tip 3/3Misleading Appearances
Being well-adjusted doesn't always mean being overtly happy or extroverted. 
Although quiet, her teachers described her as well-adjusted.