I think it depends. I have a tendency to sympathise with those who're weaker than I. If I face a dilemma where I could give either myself or others priotity, I try to rationalise it if I can miss a little something for another person. I mean, just doing something kind, just giving a little something of your time or your kindness or taking the brunt of something for somebody else could mean the world to another person, who might not be able to handle things as well. And after all, there's a bit of a rewarding feeling to prioritising others over yourself, like your brains compensates for being selfless and not giving a crud about material comforts by making you all warm and fuzzy inside.
So I guess I like to put others above my own for the warm and fuzz. :3
On the flipside, if we're talking about more serious sacrifices, hell, like giving my life, I probably wouldn't wager it. I mean, I still want to live, and be at least reasonably well off so that I can do the things I want in my life. A little bit of egotism cannot hurt, and sometimes, it's necessary if you want to act as a peacemaker between two people in a conflict. If I have to make physical sacrifices, take a bit of pain, or serious psychological damage that goes far beyond the "Yay, I feel all warm and fuzzy for helping someone" then I will only do that for a very, very good friend.