Any tips on how i can not think like this?!

Any tips on how i can not think like this?

alright, i get really insecure about certain stuff with my boyfriend. the story i'm about to tell did not happen, but i just want to give you an idea about how i get insecure about ridiculous stuff. alright say my boyfriend loves chocolate chip cookies, but i don't have any to give him. but there is this girl who does have cookies and she's giving them out. and i think she is somewhat pretty. so if my boyfriend takes one from her, i feel that he will like her better than me even if only for that split second when he gets that cookie. okay. this would just make me extremely upset and i would feel like she is better than me. so any tips on what i can tell myself to not get jealous so easily??

I really do not know what to tell you. I get same way.