Accidents will happen
Definition 1 of 1
Pro Tip 1/3Unexpected Events
The phrase suggests that no matter how careful you are, some things can't be avoided. 
Jack fell while skating; accidents will happen.
Pro Tip 2/3Consolation
It's often used to comfort someone when something has gone wrong unintentionally. 
You didn't mean to spill the juice—accidents will happen.
Pro Tip 3/3Not Blameful
Saying 'accidents will happen' removes blame from a person who made a mistake. 
He apologized for breaking my cup, and I said accidents will happen.