Most nights, I don't so much fall asleep as pass out. But if I had a few moments of consciousness I'd like to follow the advice of Russian Orthodox saint, Theophan the Recluse*: "It is the essence of evening prayer to thank God for the day and everything that happened, both pleasant and unpleasant; to ask forgiveness for all wrongs committed, promising to improve during the next day; and to pray that God preserve you during sleep. Express all this to God from your mind and from your whole heart." Here is an Eastern Orthodox night prayer that does the job:
O Lord our God, however I have sinned this day in word, deed or thought, forgive me, for Thou art gracious and lovest mankind.
Grant me peaceful and undisturbed sleep. Send me Thy guardian angel to shield me and protect me from every evil;
for Thou art the Guardian of our souls and bodies, and unto Thee we ascribe glory, to the Father and to the Son and to the Holy Spirit, now and ever, and unto ages of ages. Amen.
* St. Theophan the Recluse (1815-1894) was a holy monk and bishop and a prolific spiritual writer. This is a picture of him...
...but I confess I am reminded of Mel Brooks' The Twelve Chairs and Dom Deluise's rascally Father Fyodor in that under-appreciated gem.