"I'm not obligated to do that."
There are two reasons people say that. One is to legitimately protect themselves from being used and abused.
The other is to be a lazy pain in the ass.
Cry all you want about special circumstances, but in my life I have come to the conclusion that these are the only two reasons. And the later version is one of the most obnoxious sentences I can hear a human being utter, because it is done for its own sake. People refrain from something they are not obligated to do simply because they are not obligated.
I have for years adopted one main metric by which I judge the quality and character of people I encounter;
How willing are they to exceed their obligations?
That means of course that unlike many in our society I don't see "fulfilling one's obligations" as an admirable trait. The fact that many people do not fulfill their obligations doesn't mean the simple act of doing so makes you a hero.
When I become upset or offended by someone failing to take an extra step for me or for someone else, it's not usually because the person "has no right" to behave that way. I'm not marching on Washington demanding that laws be changed and the Constitution be amended. I am responding to a lack of warmth or consideration on the part of people that have it within their power to make something easier for others, but opt not to because it is their right to do so.
Yet it isn't a matter of rights, despite many acting like it is so.
"I have no obligation to throw my trash away. This is McDonald's, they pay people to do it."
"I have every right to sit on this bench despite the fact the old lady in a walker would like a seat. You can't make me get up. It's a free country."
"My friend has left a voice mail, text, and email in the last few days, but this is my weekend. I don't like feeling obligated to get back to someone just because we are friends. I have personal space and have every right to kick people out of it when I feel I don't want to know what their needs are."
Well congratulations. You know your rights.
But when you choose to directly ease the job, the difficulty, the pain of someone else by doing something that you are not obligated to do you are sending the message that you feel something, somewhere outside of your skull has meaning. That there are in fact things taking place on this planet involving people other than yourself, and that there is a greater good than what you can determine with your five senses.
In short, it makes you a decent human being, when merely fulfilling your obligations does not.
Use some damn common sense. Don't sell your soul. Don't endanger yourself or your loved ones. Know your limitations and don't break the law unless it is a fundamental issue of personal conscience. But don't stop at your "obligations" either, because quite frankly, the mere obligations we have in place in our society for one another and for our community are somewhere between piss poor and non-existent.