Better luck next time
Definition 1 of 1
Pro Tip 1/3Encouragement
Used to encourage someone gently after a failure, not to mock them. 
Your attempt didn't work out? Better luck next time!
Pro Tip 2/3Not Literal
It's not about actual 'luck', but a way to wish someone success in the future. 
Didn't pass the test? Better luck next time, you'll study and do great.
Pro Tip 3/3Casual
Primarily used in informal conversations among friends or colleagues. 
Ah, you almost won that round. Better luck next time!