how to stop feeling guilty?

Feeling bad only means that you are a good person. If you don't care maybe you two can still be friends. You can try talk to him and explain that you didn't want to hurt him and still don't want to. Let him know hes a nice guy and you would still like to hang out and be friends. If you can do this and think that he can without being mislead than maybe that can help. If you think that it will make things worse then I wouldn't even suggest it to him. You did the right thing by letting him down if you didn't feel anything. Had you stayed with him because you feel bad you would have been wrong. He would have just caught more feelings and you wouldn't have been happy either.GOOD LUCK!

If you didn't feel anything you did the right thing. You actually did him a favor by breaking up (if that's what you did). He will be able to find someone who cares for him, and likewise, you will find someone who you do have true feelings for. It's OK.

Feeling a bit of guilt is human nature. Most of the time :-)

It would have probably been worse if you stuck with him and he found out you weren't really into him later. He would have felt really hurt. You also do not want to be unhappy in a relationship you are not really into. Don't worry. Everthing happens for a reason.