"In Christ = in peace" is always valid. When I accept the truth of myself, shipwrecked and saved, and give it over to the person of Jesus, I am in peace even if I don't feel at peace.
The peace that comes from God and surpasses all understanding (Phil 4:7) was wrought by Christ on the cross and does not depend on my shifting feelings and moods...The "Shalom" of Jesus is not a mere greeting but an authoritative declaration from the Son of God, a crucified word that produces the peace it proclaims.
"Therefore, having been justified by faith, we have peace with God through our Lord Jesus Christ" (Rom. 5:1).
Brennan Manning