Have you done something that you regret so much you can't forget it?

I first:
I was a middle schooler and I was in love with this girl. We were in a band together and one day it was our turn to get graded by the band teacher (male).
While we were playing, I saw the teacher touched her cheeks but she seemed like she didn't care.
I was dumb and didn't do anything.
Afterward, I cracked a joke saying she did it so that our grade would be good.
She took it seriously and went mad. True that we made up a few days after, but after that she treated me differently.
I could have been doing a scene straight out of a manga, pulling her from the teacher and saying "I won't let anyone touches you" and confess my feelings.
That was 6 years ago, my love stayed one-sided.

How about you?

[img]http://oi44.tinypic.com/1z37xvk.jpg[/img]

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