If you have decided to break up with him, here is a simple template you can use to write a breaking up letter for him.
Dearest [name],
After a lot of careful thought, I conclude we are not fit for each other. I know I should have told you this a long time ago but I have been busy. We have been arguing a lot so it would be pointless for us to continue. Besides, arguing is bad for any relationship.
There were many things that let to this decision. There are too many to mention but the bottom line is that it is time to move on. Despite all the arguments we had, I will always be here for you as your friend. Here’s hoping you have an awesome future ahead of you. After all, great things happen to great people.
You will forever leave a mark for the rest of my life. We shared a lot of great moments with each other and that will never be forgotten.
Sincerely yours,