Well, you only live once, and you're only young for a short while—so why not? Rejection is possible, sure, but if you're the least bit ambitious, then it's also a necessary part of life—especially when it comes girls. So just go for it, dude.
That being said, I'm a p**** and have never asked out a girl I didn't know all that well. But I also don't get laid too often either. So, yeah... don't be like me.
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Love was invented by guys like me, to sell nylons.