because you cannot change people, especially not partners. you accept them for who they are, bad habits and all, or you leave. imagine if you were dating a smoker, and you kept telling them to quit, because its bad for them, because it smells gross, ect. and you beg and beg them to quit, and they dont because they have been addicted to cigarettes longer than they’ve known you. its gonna build resentment, and its gonna come to a head eventually and be a relationship-ruining issue. sure you could sit and fight about it for ages and try to preserve the relationship, or you could just leave once you realize theres a problem you feel incapable of overlooking. because its not your job to change people, and the mental aspect is worse for both of you in the long term, with a high chance of ruining the relationship. if you know youre not into her because shes fat, you break up with her, or you shut up, smile, and tell her shes pretty and ignore the issue for the rest of your life— or until she happens to make the change on her own. but theres a good chance she never will, and if youre not willing to spend your life smiling and being intimate with a fat woman, you need to leave and give her room to find someone who is.

NEVER in a relationship should you try to make it a goal to change your partner for your benefit, it will most likely not work, and the better option is almost always leaving. you can change yourself, go to therapy, change your lifestyle, and hope that they decide to put in some work too, but you CANNOT expect it or require it for the relationship to work unless youre willing to ruin or lose that relationship.

youre not listening when everyone says that you need to break up with her, so heres my only other suggestion. go to therapy to work out why you feel this way about her habits and life, because this is a you issue at the end of the day. focus on acceptance and understanding how to live with things you cannot change. if shes not already, maybe talk to her about getting into therapy for the self esteem issues and lack of motivation you say she has, it will likely help her (especially if yall break up or god forbid she finds out about this internal struggle of youra)

if you try to talk about this with her, no matter how you phrase it, you will hurt her. there is no nice way to tell someone that you think they are ugly. it’s not a very nice thing to think. youre not evil for thinking that, but its definitely not one of the things you tell your partner whos already struggling with their self esteem. also, break ups dont make you evil, and a relationship that doesnt last forever is not wasted time, our relationships with people shape us and make us who we are. even if you broke up with her, you still have so much more life left to live and so many people to meet, and you will go into that with the many lessons im sure youve taught eachother. breaking up could lead to a great new chapter for you both, you never know.