why is it that those closest to you are the ones that hurt you the most?

why is it that those closest to you are the ones that hurt you the most? its no like they mean to but that doesnt mean it hurts any less...for them to even think the things they do it has to come from somewhere....and theyll apologize all day but never actually take it back...they meant what they said.. they just didnt mean to say it...ugh i dont know what to do...one of my closest friends said something that upset me pretty bad but i didnt let it show too much. and they apologized. but they still meant it...she was genuinely upset that she made me upset...not at what she said though...and this from someone i thought i might have feelings for...it made me realize that im not someone she would date...and ive been thinking about my feelings toward her for quite a while now...and to know that theres no chance is not a good feeling. the first person i allow myself to feel for and this happens...in high school i didnt care and now i dont really have the time because of school but now im starting to care that im alone...and then this...im beginning to think that im just meant to be alone...ugh! i need to go through my DA page and take a lot of what ive written down......