In order to be happy we must first possess inner contentment; and inner contentment doesn't come from having all we want; but rather from wanting and appreciating being grateful for all we have.
The universe that we inhabit and our shared perception of it are the results of a common karma. Likewise, the places that we will experience in future rebirths will be the outcome of the karma that we share with the other beings living there. The actions of each of us, human or nonhuman, have contributed to the world in which we live. We all have a common responsibility for our world and are connected with everything in it.
The purpose of our lives is to be happy. We live in hope, which means looking forward to something good. And there are increasing scientific findings that both our physical and mental well-being depend on our peace of mind.
It is felt that a disciplined mind leads to happiness and an undisciplined mind leads to suffering, and in fact it is said that bringing about discipline within one's mind is the essence of the Buddha's teaching.
I feel that a genuine, affectionate smile is very important in our day-to-day lives. How one creates that smile largely depends on one's own attitude. It is illogical to expect smiles from others if one does not smile oneself. Therefore, one can see that many things depend on one's own behaviour.