If you’re going to write a letter to your ex-girlfriend, proofreading is important. We don’t know why they broke up, but there must have been a good reason for it, and we bet this girl doesn’t need any more reasons to be upset with her ex. She is mad enough as it is, so it doesn’t seem like giving her a letter full of mistakes will make anything better.
This goes to show they probably made the right decision breaking up, since this guy probably doesn’t know his girlfriend too well – he should’ve known better than sending her an apology letter full of mistakes. After reading the whole thing thoroughly, she finally graded his paper D-, letting him know there’s a lot to work on (not in their relationship, but his grammar).