It’s from his high school years. McCullough writes, “He memorized a prayer, one he would say through much of his life,” then quotes
what I call “Truman’s Integrity Prayer.”
Oh Almighty and Everlasting God.
Creator of Heaven, Earth, and the Universe:
Help me to be, to think, to act what is right,
because it is right;
Make me truthful, honest and honorable in all things;
Make me intellectually honest for the sake of right and honor
and without thought of reward to me.
Give me the ability to be charitable, forgiving and patient with my fellowmen –
help me to understand their motives and their shortcomings –
even as Thou understandest mine!
Amen, Amen, Amen.
from Truman the biography.