tappin' the bomb 

1: (hypothetical) used to express the desire to go back in time and change a single moment in your life, hoping that the new timeline will turn out better.

2: (altruistic) sacrificing yourself to satisfy someone else's needs whether the results benefit you or not. Used to describe literal sacrifices of life or happiness or simple compromises for someone you care for but don't agree with.

Comes from a scene in the fifth season finale (and sixth season premiere) of LOST wherein the character of Juliet--knowing that her death is imminent--quite literally taps the core of an atomic bomb, hoping to create a time paradox and better the lives of her friends. She does this even though not only will she die but also an alternate version of her would not ever meet her soulmate.

The term itself was coined by LOST creator and producer Damon Lindelof in the audio commentary track of the premiere episode on the first disc of the sixth season DVD set of LOST.

Damon: I really need to tap the bomb and not have married you.

Husband: I tapped the bomb for you and let you watch that cooking show when LOST was on.
Wife: Oh don't be such a martyr.

American Man: Uh...what are you doing to the core of that atomic bomb?
Japanese Man: I'm tappin' the bomb to try to go back in time and stop you assbutts from killing my family.

tappin' the bomb by Tav El December 22, 2010