“The moral purpose of a man’s life is the achievement of his own happiness.” — Ayn Rand *
To hold one’s life as the highest value is to be egoistic (that is self-interested, and self-ish).
Self-interest (egoism) means to hold one’s life as the ultimate standard of value (the measure by which one determines and judges one’s actions), regarding oneself as the primary beneficiary of one’s actions.
However, egoism is not an out-of-context concept but to be valid (i.e., truly egoistic and not self-destructive) egoism must be guided not by whims or unanalyzed emotions, but by reason.
Self-interest indicates the end (the self) of one’s actions; rational indicates the means (reason) of obtaining that end.
What objectively bridges the two is a rational code of moral principles that serve as one’s guide to action.
Rational self-interest means choosing to take those actions required by a human being, according to a reality-based, objectively validated moral code of values, so that one may live a flourishing life on earth.
In regards to one’s relationship with others, rational self-interest does not mean sacrificing oneself for others (what philosopher Auguste Comte coined as altruism or “otherism”) or sacrificing others for oneself (what is smeared as “selfishness”). Instead, rational self-interest means having a benevolent view of existence, seeing other individuals as traders with a shared harmony of interests, exchanging value for value — in the material (wealth and pleasure), intellectual (knowledge and discussion) and spiritual (love and friendship) realms.
*Ayn Rand “The Ethics of Emergencies” The Virtue of Selfishness 49