Why do I feel bad when I don't give money to bums

Yesterday as I was leaving Walgreens, I was approached by a homeless man who was selling one of those newspapers that homeless people distribute. I have no idea who thought that this was a good way to empower the homeless. But anyway, I told the man that I was sorry, but I didn't have any change for him (which was a lie), and started walking away. At that point, an amazing guilt started to come over me. I live so comfortably, but this man clearly doesn't. A lot of homeless people are in their dire straits because of mental illness, or a difficult financial situation. At the same time, it's not like I can help everyone. Why do I have to feel guilty for walking past a homeless man without giving a handout? Everyone else does it.

Well, needless to say, my conscience eventually got the best of me, and I went back to give the homeless man some money. Since I was feeling guilty from my internal debate, I gave the man a whole dollar instead of just some change.

When I finally got home I was sad to see that I must have had a hard time seeing in the dark, because I had actually gave the man a hundred dollar bill! I guess I'll be eating canned soup the next few nights.