What we do for ourselves dies with us. What we do for others and the world remains and is immortal.
I was reading an article from Psychology Today recently and it talked about the positive correlation of helping and doing good for others with happiness in the brain. There is now neural evidence showing the link between giving and happiness in our brains. So, in helping others we are also helping ourselves. By doing good for someone else, we increase our well-being and we lower depression.
Aside from our own positive benefits, doing good for others by being kind, or lending a helping hand as Albert Pike says "remains and is immortal". We can change someone's life in one simple act, and that in turn can cascade and help others in positive ways. In a sense that one kind act lives on far after we will, and remain in this world.