The way of the world
Definition 1 of 2
Pro Tip 1/3Unchangeable Reality
Refers to things beyond our control and must be accepted as they are. 
People will always seek their own advantage; it's the way of the world.
Pro Tip 2/3Resigned Acceptance
Used when acknowledging that a situation, often negative, cannot be changed. 
He sighed and said, 'I guess that's just the way of the world.'
Pro Tip 3/3Unsentimental Truth
Expresses a pragmatic viewpoint, without idealism. 
In business, profits matter above all else; that's the way of the world.