Open-source anxiety

Ever since i started coding, i have open-source anxiety, i could just never understand people who would publish their sweat and tears with only hope of some little eetsy tiny little license. I mean someone could just copy and modify it a bit, right?

Right now i created really cool C++ libary, I Mean it's not gonna be next Facebook, but i think it will help decent amount of developers and will look good on my resume, my brain just can't comprehend why wouldn't somebody be able to steal the solution to the problem it solves.