1
general::
In a state of agreement or friendliness, not at strife or war; also, in a state of inner harmony or quiet. For example, Whatever their disagreements, Mexico and Belize have remained at peace, or In his last illness he seemed finally to be at peace with himself. [1300s]
American Heritage Idioms
2
general::
Phrase(s): at peace
1. relaxed and happy. • I am always at peace when I sit in my rocking chair. • When the warm breeze is blowing, I am at peace. 2. Euph. dead. • It was a long illness, but she is at peace now. • At last, Uncle George is at peace.
McGrawhill's American Idioms And Phrasal Verbs