Just from having seen you around for a while now, you wanted to ctb for various reasons even before knowing this guy?
So I don't feel like you want to ctb because of him. I think you formed a connection/attachment that maybe made your days feel a little more bearable or at least shook up your routine a bit/made you smile more/gave you something to look forward to.
Losing that suddenly, you miss it, and that's only natural. It's natural for everyone. But if you have some kind of underlying personality disorder or attachment issues then yeah, a rejection can feel like the end of the world until you've processed the emotions. It's easy to say "it's dumb" when you have a neurotypical thought process. When you don't, the emotions are very real and can be very intense (even if you can apply logic and understand that the likelihood is you're overreacting to a situation - doesn't change the "feelings").
When I have a heightened emotional response I instantly want to ctb. Reading into a comment made a work where I "perceive" criticism, even if it wasn't intended and is a misperception, I want to ctb, I'll play out conversations over and over in my head and stress over where I might have offended someone and - you guessed it - want to ctb. And these are, I know, relatively small things as water off a ducks back to most people. So you can imagine what I feel like when I lose an important friendship or have a relationship breakdown.
To be fair, these days I'm much better at my emotional regulation than I was in my teens and early twenties but it took me bloody years of practice.
So no: it's not dumb, your emotions are not "dumb", they're valid, but it is impulsive, and it will likely fade in a short time. Hence always encouraging people who seem in crisis reactive to a recent event to wait. X