he's a nice guy

often  after a date i will tell  friends or the person who set me up with them that the guy is a really nice person but he is not for me.  i mean it. both parts. he  really is a nice guy AND he is really not for me. this always confuses people. if i think he is a nice guy why do i not want to go out with him  again? i don't mean to be confusing, its just that though i think the guy is a good person there are things about him that i dislike/can't live with and therefore do not want to continue with him. does my not wanting to date him mean that i have to say that i think he is a dreadful human being? i know  that if i would say that every guy i don't want to date is dreadful  that would not go over well either. then i would be the woman who can't stand every man who is sent her way.  even though i don't want to continue dating someone  i don't want to diminish his dating prospects by saying lashon hara i don't believe about him just to shut people up  . i suppose i will continue to confuse people . its what i do best. after all i am a woman.