Decompression.
From The power of lonely – The Boston Globe:
The teenagers weren’t necessarily happier when they were alone; adolescence, after all, can be a particularly tough time to be separated from the group. But Larson found something interesting: On average, the kids in his sample felt better after they spent some time alone than they did before. Furthermore, he found that kids who spent between 25 and 45 percent of their nonclass time alone tended to have more positive emotions over the course of the weeklong study than their more socially active peers, were more successful in school and were less likely to self-report depression.