I wouldn't say a crush can do any major damage to your well being. It's when you fall in love with that person, and it's not returned that the real heartbreak starts. I had crushes and 'girlfriends' in high school, but It actually didn't happen to me until I was in my early 20s, when I really understood the nature of a relationship. It completely ruined me.
If you feel like you're getting to a point where thinking about not being with this person makes you physically sick, the only thin I can suggest is avoidance.
Sometimes people just aren't good for each other. Not assuming this is the OP's case, but it's a possibility.
OP, just try to keep away from that person for a while until the feelings die down. Find something else to occupy your time with that isn't this person, you don't want jealousy to tear away whatever friendship you have.
Useless... Wait where's Nintendo ID on here?!?
Here's an idea: Dating as a teen is completely pointless. I believe it was about 20% of people who date in high school actually marry. Way lower number than it seems. Get over the crush and avoid dating altogether till your older-ish.
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