Schopenhauer explains the heart of his philosophy is to “disown” life and this renunciation is the ultimate basis for his instruction on happiness:
He who has taken to heart the teaching of my philosophy–who knows, therefore, that our whole existence is something which had better not have been, and that to disown and disclaim it is the highest wisdom–he will have no great expectations from anything or any condition in life: he will spend passion upon nothing in the world, nor lament over-much if he fails in any of his undertakings.
There are various ways to understand Schopenhauer at this point. He admittedly derived a great deal of this his thinking on this point from Eastern religion, particularly Buddhism. I wish to be careful here, because my knowledge of Buddhism and Hinduism is limited. However, a few citations may help explicate some of the background on his instruction in happiness at this point. For those who would like to take a dive into his relationship to Buddhism, here is an essay from Peter Abelsen, Philosophy East&West Volume 43, Number 2, April 1993. 255-278, entitled, “Schopenhauer and Buddhism” http://www.ahandfulofleaves.org/documents/Articles/Schopenhauer%20and%20Buddhism_PEW_Abelsen_1993.pdf
Here are some quick citations which provide a quick background to the topic:
With the self unattached to the external contacts he discovers happiness in the Self; with the self engaged in the meditation of Brahman he attains to the endless happiness. Bhagavad-Gita 5.21
Kesava Kasmiri’s Commentary on this verse states:
If a person is inclined to attachment to sensual pleasures they will never have the opportunity to experience the transcendental bliss of the realisation of the Brahman or the spiritual substratum pervading all existence. But a question may be raised what happiness can a person derive from life if they have introverted their senses and are averted to sense objects. Lord Krishna states the compound words sukham-aksayam meaning unlimited happiness is what such persons attains for with disconnection to the senses and objects of the senses a natural detachment arises which frees one from worldly desires allowing one to focus within on the eternal atma or eternal soul where one tastes boundless joy and experiences unlimited bliss. In the moksadharma section of the Mahabharata it states that: The pleasures of the senses in this world and the joys of heavenly pleasures cannot be compared to even 1/16th part of the pleasure one derives from renouncing the desire for material sense gratification. This is the essential component that paves the way for perceiving the Brahman or spiritual substratum pervading all existence, atma tattva or realisation of the soul and moksa or liberation from the material existence and cognition of the ultimate truth of the Supreme Being.
The concept of renunciation is central to Buddhism. Schopenhauer’s connection between happiness and renunciation is articulated within Buddhism as for instance in this essay, “Renunciation and Happiness”:
When we understand this, we can start to glimpse that renunciation is not a matter of doing something or having to create something, or getting rid of something or exterminating something in life. Rather it is moving towards non-contention, a sense of rest and relaxation—not having constantly to try and manipulate and control and evade and maneuver any more. We are able to open in a fearless way and relax into the experience of the moment, whatever its quality may be. In opening to receive life, we still engage in the conventional level of reality—the social level of moral values, indentities, mother and father, livelihood and mortgages. If we grasp these things and expect complete fulfillment from them, we will always be disappointed. But if we see our life as an opportunity to understand Dhamma—the way things are—that is renunciation. This letting go is very freeing. Whatever comes to us is Dhamma, and there is a joy in being in contact with Truth, whatever its particular flavor.
Renunciation can sound like passivity, a “door mat” philosophy, but actually it is the opposite. True response-ability—the ability to respond wisely and compassionately to life—naturally arises in the non-attached mind. There can be both activity and letting go.
https://www.buddhistinquiry.org/article/renunciation-the-high-happiness/ I would be curious to know whether the precise concept of “happiness” was connected to the concept of renunciation prior to extensive Western contacts. Schopenhauer obviously is drawing a connection between renunciation and happiness. What I do not know is whether Schopenhauer is first in tying the two concepts together. Certainly there is a connection between tranquility and renunciation which pre-exists Western interaction; but whether this tranquility and “happiness” was drawn I simply do not know.