Is having an erection good or bad when grinding with girl?

ok so i just had my junior prom and it started off great. we were grinding alot and i got an erection(kind of the first time i was really grinding with a girl). it seemed like she liked it because she started pushing up against me more. everything was going good and i thought it was ok to get an erection whenever i grinded with her. so then everything went good until the last hour. she started pushing up against me less(WITH ERECTION) then 2 times she suddenly stopped and said she was thirsty or had to go to the bathroom.(this girl always dances by the way. then me her and 2 other people were talking together and her friend(A GIRL) called her up to dance. i went to go with her and then she kinda waved me away and said she would be right back. after that she seemed a little weird and we didnt dance at all for the rest. im just really confused because i dont know how it went so good for most of the time then just bad the last hour.....please answer honestly and i appreciate both guys and girls to answer....thanks!Is having an erection good or bad when grinding with girl?
if a guy got one while i was dancing with him i wouldnt see a problem, its kind of expected if your rubbing up against there right? she probably wanted to spend time with other people at the dance as well. dont worry :)Is having an erection good or bad when grinding with girl?
Grinding is in no way a form of dance. The fact that you were erect says that your mind was not on dancing. Guys seem to think that all girls are easy, which is not true. Lesson #1 ...... dancing is for the dance floor,,,,,erections r for the bedroom!

Lesson #2.....there is no brain in your penis. All girls know that.

So if you have a brain, start using it!
ummmmm....... well i supose its nothing to be ashamed of cause it happens like most of the guys i have grinded with have had it happen (i am a girl by the way)

maybe something happened with her friend (drama) lol
You did everything just fine. Yes, thats 1000% normal. Maybe- and I'm just guessing- she enjoyed herself but wnated you to cool off. Thats all. Have you talked to her lately?