Greed is an impulse in us that wants to gather things to ourselves. Kindness is an impulse in us that wants to share things. They go in opposite directions, and have very different mental health consequences.
Greed has its roots in our evolution. Evolution is really no more, in principle, than the idea that those organisms without a quality died, and those with it survived. One can see how organisms with individual greed might survive reasonably well in the short term. Each organism gains some consistency in terms of food and lodging, by chasing away anyone who threatens it.
However, in the end, a group of greedy beings will come up against a group of kinder beings, who are able to share with each other. One can see how kindness can survive reasonably well. The group of greedy individuals might suffer through the lack of a mutual store of goodwill and supplies. The group of kinder beings might survive through a more universally generous approach to each other.
We live, though, in a civilised world beyond mere evolution, in which many groups of humans survive regardless. People have become quite good at ensuring mutual survival, and have built legal systems which prevent too much intra-society conflict.
Greed versus kindness has become a personal decision, which we can take each morning. Under both tactics we will usually survive, so it is not as much a matter of biological life and death as it used to be.
But there is a subtle psychological reality underlying all this. If we pay attention to our own inner happiness, we might notice that greed hurts, and kindness doesn’t. Resentment hurts, and generosity doesn’t. Bitterness hurts, and and forgiveness doesn’t.
My body and mind are inherited from millions of years of history. My potential behaviours have their roots in generations of successful groups of beings.
But, sooner or later, I make choices about my behaviour.
In particular, I choose whether to try to grasp all things for myself, or share all things with others.
The outer world may not notice which I have chosen.
But I will notice. Suffering will tell me when I have chosen greed, and happiness will tell me when I have chosen kindness.