People going through the most difficult trials will form the strongest of bonds.
Honestly, this is one reason I think religion and vice often flourish where they are illegal.
Remember: Worthwhile common goals bring us together.
It is little surprise that few care about an involuntary group formed at work – and elite soldiers frequently give their lives for each other…
Now the harassments, the exertions, even the beatings of initiation rituals begin to make sense. The Thonga tribesman watching, with tears in his eyes, his ten-year-old son tremble through a night on the cold ground of the “yard of mysteries,” the college sophomore punctuating his Hell Night paddling of his fraternity “little brother” with bursts of nervous laughter—these are not acts of sadism. They are acts of group survival. They function, oddly enough, to spur future society members to find the group more attractive and worthwhile. As long as it is the case that people like and believe in what they have struggled to get, these groups will continue to arrange effortful and troublesome initiation rites. The loyalty and dedication of those who emerge will increase to a great degree the chances of group cohesiveness and survival. Indeed, one study of fifty-four tribal cultures found that those with the most dramatic and stringent initiation ceremonies were those with the greatest group solidarity.
-Robert Cialdini, Influence