I care about him sm

I meet a new boy and this time hes so kind, he feels the same way with me and im so scared cause I don't want him leaving me. I want to detach cause I don't wanna be upset if he leaves me and I hate that im afraid to feel happy about this. im so used to boys not liking me back so maybe that's why but I don't want to ruin this one good thing I have. I always end up ruining the good things.