One has to learn tolerance in the face of dualities such as happiness and distress, or cold and warmth, and by tolerating such dualities become free from anxieties regarding gain and loss.
Bhagavad Gita 2.45,
"Accept Krishna as your friend. You will be happy." This is the message of Krishna Consciousness.
Civilization and Transcendence,
The spirit soul can be happy only in the association of the supreme living being, the Personality of Godhead, and nowhere else.
Srimad Bhagavatam 3.2.11,
The more we are happy in Krishna Consciousness the more we become purified.
Actual joy is a product of the spiritual nature. It spontaneously manifests when the living entity begins to love God.
We are like fish out of water. Just as a fish cannot be happy unless he is in the water, we cannot be happy apart from the spiritual world.