The fundamental need of every living being is to love and to be loved. Without that nothing can really satisfy the heart.
Objects can satisfy the senses of the body. Various emotional gratifications can satisfy the mind. But the heart is yearning, longing, to love and to be loved.
In the Brahma-sutra it is said ananda-mayo 'bhyasat, which means the inherent nature of every living being is we are seeking pleasure.
It is something we all have in common.
Even the little ant that is crawling on the floor is seeking pleasure in a particle of sugar.
The procreation of all living beings is based on that longing for pleasure.
But only love can give pleasure to the heart.
And we can see for example in a child, if a child is given a beautiful home, wonderful toys and games, but that child does not feel loved, the child will be insecure, unstable and unsatisfied.
It is our nature, whether we are black or white or red or yellow in color, whether we're American or Russian or Indian or Pakistani or Palestinian or Israeli, whether we're young or old, rich or poor..
Whatever our particular designation may be in this world, our inherent need is to express and feel love for someone else and to feel loved by someone else.
Why is it that we all have that in common?
According to the Srimad Bhagavatam it is because it is the inherent nature of the soul. The soul is part of God.
Nitya-siddha krsna-prema sadhya kabhu naya / sravavadi-suddha-citte karaye udaya (Sri Caitanya Caritamrta Madhya 22.107)
That love of God is dormant within the heart of every living being, but we have forgotten that love.
So we're trying to find that experience of pleasure in so many ways in this world. And because it's not really satisfying our need, so much frustration.
And due to that frustration human beings can act in such strange and often dangerous ways, to themselves, to others and to the planet.
It's all in the search of love.
So the purpose of life is to redirect that propensity to love, of the soul, back toward God.
And when we experience God's unlimited love and we feel the unlimited love of the soul for God, included within that experience is compassion and love for every living being.
That is what everyone is looking for.
That is the essence of every religion.
And that is the highest purpose of life.