<human>: Throwaway for obvious reasons.

For context, I go to a university now on the other side of the state from the girl mentioned in the title.

I had always had a crush on this girl, we'll call her Firetruck. She went on a Mediterranean cruise, and I was going to confess my feelings for her when she got back. In that time though, a girl I knew was interested in me (and whom I should've known to avoid, and whom we'll call Ambulance) called me up and I ended up with her before Firetruck even got back. It was mostly because I was unbelievably scared of losing her (Firetruck's) friendship over it, so it was sort of the easy way out. Ambulance goes on to crush my heart, and Firetruck slowly talks to me less and less as I let Ambulance slowly destroy my entire being and self identity. 

Today, I was having lunch with a friend from highschool, and I mentioned to her that I had a crush on Firetruck all throughout highschool and that sometimes I see a picture she's uploaded to facebook and a little pang of regret runs through me at what could've been. The friend who I was having lunch with responded as follows:
"I never knew you felt that way about Firetruck. She's been basically madly in love with you for as long as I can remember."

Suddenly, I have found my biggest regret of all time, not knowing what could have been. 

What is your biggest regret from high school?

Could you distill the essence of the text into 1-3 sentences?
<bot>: I'm an idiot and decided to date a girl who was a life sucking vampire instead of being ballsy enough to confess my feelings to the girl of my dreams