One who is ignorant of scientific knowledge of the spirit soul does not look inside the body to find happiness in the soul; instead, he goes outside to search for happiness
Srimad bhagavatam 7.13.29,
Everyone is hankering for happiness because by nature we are happy : anandamayo 'bhyasat (Vedanta-sutra 1.1.12). As spirit souls we are naturally happy, blissful.
There is no peace or happiness in our worldy life. Circumstances create turmoil and annoyance.
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,
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,
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.