attachment issues

people on the internet always joke about attachment issues but its is actual hell i cannot move on from someone even though i have a very GOOD reason to i know the reason i repeat the reason in my head over and over but i cant seem to get over it i just go back to the good memories we had that i glorified in my head and no matter how self aware i am i always fall back into the same hole of missing them and its torture i cant snap out of it i cant just stop i cant do anything else thank god i had someone to knock me to my senses because i cannot trust myself or my feelings at all i dont know if i am overreacting or not i can never know i am stuck in my own head all the time overthinking the same things feeling horrible over and over like i need them right now or i'll die like i made a huge mistake like something is missing i feel flashes of anxiety and it makes me  nauseous but in reality everything was fine i am eating dinner with my parents i have good friends i dont hate life everything is ok but my head tells me otherwise when they tell u ur issues are all in ur head it might me true for me but i cant seem to escape it