Upekkha, or equanimity
"All beings are the owners of their karma. Their happiness and unhappiness depend on their actions, not on my wishes for them."
I try to remind myself of this everytime things don't go the way I want them to. We have no control over anyone. Nor should we seek to control anyone, no matter how much we believe it's for their own good, or that we know better.
And note to anyone who's reading this: if your friend is gay, don't fucking try to matchmake him/her with someone of the opposite sex. Just because you feel bad that your gay friend will never enjoy parenthood/marriage/giving birth (now, is that something you want to miss??!)
Allow your friends their own choices.