We hate others who are selfish, but justify ourselves when the same feature(selfishness)is within us. Lack of sympathy has been seen as one of the roots of selfishness. This trait puts an ugly mark on the soul of an individual. Some selfish people treat others as an option when ever they require some favour from them. After their work is over they treat them like strangers.
In Mahabharat an Indian epic, Duryodana, son of Dhritharastra, the king of Kourava Dynasty, supported Karna, who was son of low caste person ie., Sutha in a tournament with his selfish motive. Karna an Archer was not allowed to show case his skills on the basis of his caste. Duryodana with his selfish motive crowned Karna as king of a small country called Anga, to take revenge against pandavas who are sons of King Pandu, as he desperately wanted a good Archer on his side to match Arjuna.
Likewise in Ramayana an Indian epic, there is an instance of selfishness which showed drastic effect on the family of king Dasaradha of Ayodhya. King Dasaradha promised two boons to his third queen Kaikeyi as she helped him in a war. When Dasaradha wants to make Rama,who was his elder son through his first queen Kousalya, as king of Ayodhya, Queen Kaikeyi asked Dasaradha to send Rama to forests for 14 years and make his son Bharatha as king of Ayodhya to fulfil her two boons.The first boon tormented much Dasaradha to send his beloved son Rama to forests.
The result of her selfishness caused the death of King Dasaratha, who cannot bear the pain, and it also resulted hatredness towards Kaikeyi by her own son Bharatha, whom she wants to make him as crown prince of Ayodhya.
Now coming to the present days this trait in humans is in full swing in all walks of life. For example suppose there was an interview with regard to a post in which 10 candidates appeared for the examination.
In which X a poor boy stood first and Y not even secured the required marks. The father of Y who was rich and influential person managesd to get the job for his son, by influencing or bribing the selecting officer. Does his act is not selfish? Not even himself selfish but also the Selection Officer. Is it not a blow on the livelihood of the poor boy and his family? Temporarily they may enjoy the fruits of their Selfishness, but Nature won't keep quite. It takes its own course of action in due course. It may be in the shape of a disease, accident, loss of property etc. Many people are not aware of the consequences of their selfishnes.
Sibichakravarthi, a king in Hindu mythology was renowned for his selflessness and is said to have saved Agni from Indra, when they appeared before him to test his selflessness, by transforming themselves like dove and hawk respectively, by offering up his own flesh from his thighs.
We are now living in Kaliyuga and may not be possible to offer our flesh for others, but we can live selflessly with more concern of the needs and wishes of others than with our own. To know or to develop the said quality in us we have to approach a Sadguru to free ourselves from all the vices including this selfishness and fly freely towards the Ultimate( God) averting the fall with in the cycle of birth and deaths.