This post was originally published on Wait But Why.

When you’re a kid, or in high school or college, you usually don’t work too hard on your friend situations. Friends just kind of happen.

For a bunch of years, you’re in a certain life your parents chose for you, and so are other people, and none of you have that much on your plates, so friendships inevitably form. Then in college, you’re in the perfect friend-making environment, one that hits all three ingredients sociologists consider necessary for close friendships to develop: “proximity; repeated, unplanned interactions; and a setting that encourages people to let their guard down and confide in each other.” More friendships happen.