As quoted in Plenty of Time to Sleep When You're Dead : A Compilation of Life-changing Quotes (2006) by Richard Caridi
As quoted in Sprituality in a Materialistic World (2008) by Leslie Klein
Variant: Remember happiness doesn't depend on who you are or what you have; it depends solely upon what you think.
“All happiness or unhappiness solely depends upon the quality of the object to which we are attached by love.”
I, 9; translation by W. Hale White (Revised by Amelia Hutchison Stirling)
On the Improvement of the Understanding (1662)
Original
Tota felicitas aut infelicitas in hoc solo sita est; videlicet in qualitate obiecti, cui adhaeremus amore.
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Baruch Spinoza 210
Dutch philosopher 1632–1677Related quotes

“The happiness of your life depends upon the quality of your thoughts; therefore guard accordingly.”
Variant: The happiness of your life depends upon the quality of your thoughts.
Source: Meditations

Speech of 1877-06-24
1870s
Daniel Katz (1964) ""The motivational basis of organizational behavior". In: Behavioral science, 1964. p. 132
Source: The Functions of the Executive (1938), p. 282

Ideology and Utopia (1929)
Context: This first non-evaluative insight into history does not inevitably lead to relativism, but rather to relationism. Knowledge, as seen in the light of the total conception of ideology, is by no means an illusory experience, for ideology in its relational concept is not at all identical with illusion. Knowledge arising out of our experience in actual life situations, though not absolute, is knowledge none the less. The norms arising out of such actual life situations do not exist in a social vacuum, but are effective as real sanctions for conduct. Relationism signifies merely that all of the elements of meaning in a given situation have reference to one another and derive their significance from this reciprocal interrelationship in a given frame of thought. Such a system of meanings is possible and valid only in a given type of historical existence, to which, for a time, it furnishes appropriate expression. When the social situation changes, the system of norms to which it had previously given birth ceases to be in harmony with it. The same estrangement goes on with reference to knowledge and to the historical perspective. All knowledge is oriented toward some object and is influenced in its approach by the nature of the object with which it is pre-occupied. But the mode of approach to the object to be known is dependent upon the nature of the knower.

“Our feeling about every obligation depends in each case upon the spirit in which the benefit is conferred; we weigh not the bulk of the gift, but the quality of the good-will which prompted it.”
Eo animo quidque debetur quo datur, nec quantum sit sed a quali profectum voluntate perpenditur.
Alternate translation: The spirit in which a thing is given determines that in which the debt is acknowledged; it's the intention, not the face-value of the gift, that's weighed. (translator unknown).
Source: Epistulae Morales ad Lucilium (Moral Letters to Lucilius), Letter LXXXI: On benefits, Line 6

“The value and quality of any love is determined solely by the lover himself.”
Source: The Ballad of the Sad Café and Other Stories