It happens

It's a more socially acceptable version of "shit happens". It can be used to: 1)express condolences for someone's situation without offering any apologetic words. 2)respond to a future problems that shows a sense of sadness/aggression towards it, but in a way without trying to complain 3)to shrug off a one's own, or someone else's, minor annoyance 4)substitute for an actual response, while still continuing the conversation