what is it exactly that you want to know? 'cheating people and hurting their feelings' or 'cheating people WITHOUT hurting their feelings'? I hope you mean the latter one.. Nonetheless, you don't have to cheat people or someone you have an intimate relation with. However you look at cheating, it's still cheating and would definitely hurt someone's feelings. no other good thing but to define your reason when saying "NO" or "Forgetting Relations". People might understand your feeling as well by doing this. (You have to look out not to hurt feelings). :)

Oops! U wanna cheat people and hurt their feelings! What a mess?! I might haven't told u the answer if I had the best answer for that question. But for the other question, forget relation: this is easy, u just declare that u don't wanna be in touch anymore with the one u wanna end his/her relation.