Note this prayer is particularly relevant for someone who had an understanding of the Buddhist teachings on death

Through your blessing, grace, and guidance, through the power of the light that streams from you:
May all my negative karma, destructive emotions, obscurations, and blockages be purified and removed,
May I know myself forgiven for all the harm I may have thought and done,
May I accomplish this profound practice of phowa, and die a good and peaceful death,
And through the triumph of my death, may I be able to benefit all other beings, living or dead

Prayer adapted from The Tibetan Book of the Dead, by Sogyal Rinpoche in Tibetan Book of Living and Dying