Prayer to the Honorable Cross
Or briefly:
Guard me, O Lord, by the power of Thy holy and life-giving Cross, and keep me from all evil.
Then instead of forgiveness:
Remit, pardon, forgive, O God, our offenses, both voluntary and involuntary, in deed and word, in knowledge and ignorance, by day and by night, in mind and thought; forgive us all things, for Thou art good and the Lover of mankind.