Straight up though the truth of the matter is that crushes are really no big deal. It obviously doesn't seem like it when you're Facebook stalking him/her twenty times a day, but crushes are weird and obsessive like that. On one hand maybe you'll like someone for few months and then suddenly stop and wonder what you saw in them, on the other hand you might find out that that person likes you back and either a) go out with them for a while and then break up or b) end up spending the rest of your life with them. While the b) part of the latter option is probably ideal, a study I just made up (that is mostly based on common sense and also experience) shows that most crushes result in the former scenario. So there's really not much to worry about other than the standard trifecta of side effects i.e. stalkery, fakery and who's-that-bitch-he's-talking-to-she's-gonna-get-cut-ery.
But it's because crushes are so weird and obsessive that sometimes they border on being delusional. I think the number one thing teenagers and people in general need to remember is that the way we think about people and the way we imagine people is not the way they actually are. When we like someone, that person could do the stupidest thing and we'd still find an excuse to make for him or her. The number of girls I know who, in Year 9, let boys they liked copy their homework is a bit disturbing. And that's not to say I'm not guilty, I've done the same thing, and more than once. I don't really regret it now, because it was relatively harmless and also because I still claim responsibility for them not failing math that year, but I do think it's scary how willing we are to compromise ourselves for people who's personalities we build in our imaginations and who's actions we view with totally clouded judgment. Not that there's a solution for this or anything, it's just something that's useful to be aware of, even in the most intense of crushes.
It's important not to let people define you, and it's important not to let people take advantage of you. Which is why you should never let crushes get the best of you. I sound way harsh, but it has to be said, especially to young people. But for the most part, crushes are harmless and pretty exciting. When you're over them all that time spent doing your hair and fake-bumping into him/her in hallways will seem like a waste of time, but the truth that no one will admit is that having a crush is so much fun. It's something to laugh about with your friends, it's something to daydream about in class and it's someone to shave your legs for (last one only applicable to the ladies). And at the end of the day, regardless of what happens or doesn't happen you'll always have "that guy with the neon braces I used to like when I was 14" to talk about at parties, which is always a plus.