All’s fair in love and war.: any conduct is permissible in certain circumstances, (often used as an excuse for deception.)
E.g. Jim cheated on the entrance exam, but he really want to get into that school, and all's fair in love and war.
In order to get Sally to go out with him, Joe lied and told her that her boyfriend was cheating on her. All's fair in love and war.
tug of war: a struggle for supremacy, a strenuous contest between two sides, either physical or figurative .
E.g. There's a constant political tug of war between the ruling parties.
Our dogs love to play tug of war with their new toys.
battle something out: to fight about something to a conclusion
E.g. The two brothers have not talked in years, we wish they just went into an alley to battle out their differences.
The Senate and the House do not agree on the bill, so they will have to battle it out and come up with a comprise.
half the battle: a significant part of a big effort
E.g. Getting through the interview was half the battle, not I have to prove myself in the position.
I have got all the ingredients for the Thanksgiving dinner, that’s half the battle won!
to dodge the bullet: to successfully avoid a very serious problem or failure
E.g. Peter dodged a bullet. He got a "D" on the final exam so he did not fail the class.
The company laid of 80% of their employees, but they kept me. I dodged that bullet.
to make peace with: to accept something (not desirable), to stop arguing with someone
E.g. He knows that he is too old to play become a professional soccer player, and he's made his peace with that.
After years of arguing, the brothers finally made peace with each other.