Dear [Name],
I want to start off by saying that I am truly sorry for my actions. I understand that I have made a mistake and I take full responsibility for it.
I understand that what I did was wrong and I regret it deeply. I was wrong to have followed you around and to have been so intrusive in your life. I know that it was not only uncomfortable for you, but also a violation of your privacy.
I know that it was wrong for me to have been so nosy and to have been so persistent in trying to find out more about you. I was wrong to have spied on you and to have made you feel uncomfortable.
I know that my actions have caused you pain and I apologize for that. I want you to know that I will never do anything like this again. I have learned from my mistake and I will make sure to respect your privacy in the future.
I hope that you can forgive me for my mistake. I want you to know that I am truly sorry and that I will never do anything like this again. I understand how wrong my actions were and I promise to never do anything like this again.
Sincerely,
[Your Name]