A benediction is a blessing — either a formal one that you might hear in a church service or an informal one that you might utter when you take any leap of faith.
The noun benediction comes from the Latin roots bene, meaning "well" and diction meaning "to speak" — literally to speak well of. Although it is most often used in the religious sense of prayer and blessing — especially a ceremonial prayer at the end of a church service — it can mean any expression of good wishes. "Good luck on the test!" the mother cried in benediction as her son set off for school.