Ask Jono: I Don't Want To Have a Showmance!
I want to say that this is NOT about a boy, simply because I don't want it to be, but it is. To explain this lifelong struggle in about 30 seconds:
I didn't really communicate with boys until a few years ago because until then they were all stupids who were manufactured out of dirt and noise on a far away planet. But as soon as I got over that, I would fall head over heels for a new one every 5 milliseconds. Now I've been crush-free for almost a year—and a showmance is threatening to occur.
This is my first time being cast in a large romantic role in a play, so having to spend all this time (under the director's instruction) with this super-nice, really adorable guy is really beginning to test my limits. And I CAN'T fall for him, because I know I'll just wind up hurt again when it doesn't work out.
Still on the wagon/ A die-hard Jono fan
For starters, Sparkler, I'm not too surprised by your shift in behavior. There are only a few basic human impulses, and this is one of the most compelling; as soon as you were like "Wait, it is fun to like boys!" your brain was like :O and decided to start making up for lost time. It's like you spent your life eating bland potato mush and finally ate a cheesecake and now you want to eat all the cheesecakes simultaneously. My point is that I'm not sure sublimating this impulse is a good idea; there's a healthier middle ground between liking zero boys ever and liking all boys at all times. But I'll come back to that.
Normally I'd say the best way to avoid falling for one specific person is to allow yourself to be attracted to other people, and to make sure you're not around him all day. The problem is that you're trying not to do the former, and you can't do the latter without dropping out of the play and leaving a note that says "Please excuse Still On The Wagon from the play because boys." You can try focusing on his negatives, or looking at him in a strictly professional way, but I'm not sure whether those will work for you (see graphic), so here are some other suggestions.
1.) Don't daydream
If you already have to spend time with this guy on stage, you can at least make sure you're not spending any additional time with him inside your brain. The more you let yourself fantasize about someone you like, the more you tend to project all kinds of positive traits onto him; you create an imaginary version of the guy who is super nice and romantic and always says the right thing, and having that fiction in your head will make it even harder to stop thinking about him. That said, I know it's hard to focus on not thinking about something—if someone tells you not to think about polar bears, polar bears will cross your mind every minute, as if you left some delicious seal meat in there. This is why you need to have other things with which to occupy yourself.
2.) Occupy yourself
If you read that link, you'll note that the people who couldn't stop thinking about polar bears were also doing nothing else. They were literally sitting in a room tasked with nothing except "don't think about polar bears," which is why they failed at it. When you're acting alongside this guy, focus on the role, not on the fact that he is adorbs; when you're not around him, keep yourself busy. I realize it sounds kind of lame to tell you to focus on school or your other extracurriculars, but you do need to focus on something else. (If you'd been falling for random dudes so often that it was problematic, it could mean you didn't have enough other stuff in your life to concentrate on.)
3.) Be logical
So this guy is nice and adorable, but is there anything substantive that makes you think you two would be good together? Is there a chance a relationship would actually work? I know it's hard to overcome Heart Feelings with Brain Thoughts, but if you'd previously been flitting from crush to crush like a hummingbird, consider: is there any future here, or is he merely full of nectar?
Whether you know the answer to that or not, I'm going to ignore your question about how not to fall for him and ask: why don't you want to? Is it that you think he'll reject you, or that you might go out a few times and it wouldn't work out? Going on a first date doesn't have to be some huge step that means you are ~OFFICIALLY DATING~; it can just be a chance to figure out if there's anything real between the two of you, or if your attraction is just a confusing mixed metaphor about cake and hummingbirds. Maybe he'll like you back, and you'll have a lot in common; maybe he won't, and you'll have closure, and you can stop wondering what might have been. I'm giving you this advice because I know rejection sucks, but being alone isn't so hot either; instead of not liking any dudes, you should want to like the right dude, and sometimes all it takes is having coffee with someone to figure out if he's the right dude or not.