Unless each person becomes Selfish, There cannot be peace and happiness on this planet.
Mahatma Gandhi, Mother Teresa & Buddha were few of the most selfish beings ever.
They each had understood the Principle of universe, i.e. The universe is interconnected. We all are part of the same God (or Supreme Consciousness).
Just like a hand does its best to feed the mouth, knowing fully well that eventually he will himself get the energy via the blood stream in due course. Or The Hand when trying to nurse an injured leg, is being selfish, knowing well that without the feet the body will not be able to walk in order to get food in future.
We all need to help the Bodily seperated fellow humans. Realize that eventually we will all become happy, once evey one else around us becomes Happy. It cannot happen that our fellow beings are in distress and we are at peace.
The great beings in fact were most selfish when they tried to help others. Because they never thought they are helping anyone other than themselves, as they saw everyone as part of same supreme being.
Go ahead Be Selfish. Help others as you help yourself. We all share a common destiny.