A quote
Thus, as I have said, your being grateful is more conducive to your own good than to your neighbour’s good. For while your neighbour has had a common, everyday experience,—namely, receiving back the gift which he had bestowed,—you have had a great experience which is the outcome of an utterly happy condition of soul,—to have felt gratitude.
Seneca·Letter 81 (§21)·trans. Gummere