Apology Letter For Accusing of Cheating
Dearest {Recipient},
I'm very sorry for accusing you of cheating on me when you've been nothing but a wonderful, supportive, and faithful partner.
I'm sorry I lashed out at you like that. The way I behaved was really inexcusable and out of line; I shouldn't have let my past experiences influence how I treat you. I'm now working on my issues so that I can be a less paranoid and more trusting {boyfriend/girlfriend/spouse}.
I hope you can find it in your heart to forgive me. If you need more time alone, I completely understand. I'll patiently wait for your {email/text/call}.
Love,
{Your Name}