The teacher who marked up your essay in red ink was the only one who read it all the way through.

Extensive corrections mean somebody read the whole thing. Indifference is silent and looks much kinder: a grade, a short comment, nothing to argue with. A page covered in marks is evidence of time spent on your work by a person who could easily have skimmed it. The sting is real, and it is not the same as unkindness.

Read the notes again before you decide how you feel about them. Take the ones that would make the next piece better and let the rest go. If a teacher does this for you, saying thank you is not a strange thing to do.