A phrase traditionally used with the aim of making people feel better, giving them the idea that a problem they suffered was unavoidable. However, it is also commonly used as a mechanism to thwart suggestions as to how to deal with a problem.
A: Damnit, the minority have spoilt it for everyone else.
B: That's life.
A: No it's not life, you tarred them all with one brush. Here's some other methods that would have led to much less inconvenience to the responsible majority.
B: Nope. Your suggestions won't work, because the minority spoiling it is a fact of life, and therefore it is unavoidable because if it wasn't, it wouldn't be a fact of life.
aka oh well,life sucks,wtf,life ain't fair,shit stinks
Biff - "What happened to your fender? Another hit and runner?"
Suz - "Ya I'm like George McFly w/ the kick me sign on my back! Sucks but that's life, right?"
A good answer for most complaints.