Apparently i [18/f] never learn. Why do we keep subjecting ourselves to torture?

My boyfriend [21/m] (now ex) left me once more last night... i honestly think this is about the 10th time he does this. And i suppose that fact alone should reassure me of the fact that hes not the one for me.. it was a long distance relationship and we kept it going for 5 years and nowww, 2 days before i go where he lives and be together for good, he leaves me... and its not the first time.. the previous 4 times that he was able to come, he left me then too... and everytime his excuse was because of insecurity, or fear that things might not be how we want them... i should have known this i knew it would happen again, yet i kept on going, he was my first love.. I was a bit insecure too you know? and a bit scared of how things will be but i chose not to focus on that and focus on the positive which were offc that after all that time we would finally see eachother and how much we love eachother and i didnt want to let my stupid insecurities come between us, but he did.. i did everything i could for this relationship i gave it my all i swear i did but in the end i am always the one being left all alone and empty... He kept telling me everytime that he doesnt deserve me and doesnt want me to end up with someone like him and everytime he just leaves me with an email, and a goodbye I know its time to let go for good... since a long time now. im sorry i just needed to vent.. Can you tell me what you guys think of all this???