For keeps
Definition 1 of 1
Pro Tip 1/3Emotional Weight
Indicates strong emotional attachment or significance when applied to personal items or relationships. 
He offered me his grandfather's watch to remember him by, it was for keeps.
Pro Tip 2/3Irrevocable Decisions
Used to describe decisions that are final and cannot be undone or changed in the future. 
When she moved abroad, it was for keeps; she wasn't planning to return.
Pro Tip 3/3In Games
Commonly used to express seriousness in games or contests, meaning the outcome has consequences or permanent rewards. 
We're playing marbles for keeps, so if you lose, you don't get them back.