The expression "Jiri-Rita" appears quite frequently in the teaching of Mahayana Buddhism, and also there are various views on its interpretation. Among them, I believe that it is most correct to understand it as "Self-interest is in the realization of others' interest."
Essence of the Buddhist philosophy is the "logic of sosoku" (coming together and dissolving into oneness). Prajna Paramita Heart Sutra preaches "form is emptiness", but it does not mean that "form" perishes to reach "emptiness", but describes the truth that "form itself is emptiness".
Similarly, "Jiri-Rita" means to perceive "self-interest" in the midst of "others' interest", which, in short, means "self-interest is others' interest". It's not a parallel relationship of "self-interest and others' interest" as according to some other views.
With this interpretation, you see that the "self" of "others' interest" does not simply mean self as a notion. It is the subject of oneself, which is the central character.
Also, the "others" in "others' interest" does not simply mean other people. It means all the objects including not only one's own body, but even "mind" among the "eyes, ears, nose, tongue, body and mind".
Applying oneself to devotion and hard work for the sake of the world, people and the society; this is in itself self-interest, or the true joy and happiness of oneself.
If one can reach such a mindset and become a real person to contribute to society and the public, he should genuinely find his life worth living.
(Source: "TKC Bulletin", January 1998)