Schneiderman's advice to Freshmen: Join things to find out where you belong.
That is excellent advice from someone over 30. Social isolation breeds all sorts of strange and unreasonable habits of mind, while social interaction helps us define ourselves, learn about ourselves, and, especially, to learn what our limits are. Isolation nurtures delusions of grandeur or delusions of inferiority, and prevents acceptance of reality.
I attended a faculty cocktail party last night, and, for some reason, the advice I had received many years ago came into my head as a shy person during boarding school: "When you enter a gathering, make sure you say hello to, or introduce yourself to, a dozen people. Then you can leave if you want to. Never act like a shmoozing politician, but it's your job to let people know that you exist. They might want to know you, or they might not. Either way, it's learning. Learning sometimes hurts."
At my age, with genteel breeding and with my life experience, it's a little silly for me to still need that reminder. People tend to enjoy and seek my company.