Apology Letter For Not Believing Person
Dear {Recipient},
I'm sorry I didn't believe you about {topic}. You were right, {fact that they said was right}. I'm sorry I even thought that you would lie to me. I was so blinded by my own biases that I wasn't willing to listen to other people.
Please forgive my stupidity. If there's anything I can do to make it up to you, let me know.
Sincerely,
{Your Name}