As a whole, creatures are selfish. I can remember growing up helping feed the cattle and watching as they would fight over the hay and feed. I have seen other animals attack one another over food. Perhaps that is why God has commanded us to "love the Lord thy God with ALL thy heart..." and to "love thy neighbor as thyself". How difficult that is!!
In order to serve God and to be what He wants us to be, we have to go against the instincts we have within us. We have to go against the "natural" response. After all we are "by nature the children of wrath" (Ephesians 2:3). As Paul said in 1 Corinthians 9:27 "But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway." Even Paul had to go against what his body wanted and submit himself to what God wanted, otherwise, he would be "a castaway".
So the next time you feel those selfish desires rising up in you, be reminded that we are to care for others the same way we care for ourselves.
Rom 12:10 "Be kindly affectioned one to another with brotherly love; in honour preferring one another;"