Lucretius, reflecting the views of Epicurus, tells us that fear of death and overarching ambition are the things that make humans unhappy.  I would add plotting, planning, getting jealous, scoring points and putting people down to that list.  Lucretius encourages us  to enjoy the wonders of the universe and the natural things before our eyes, the beauty and fecundity of the Earth and the huge variety of trees, flowers, and animals, all adapted to their environment.  And all, he says composed of atoms, morphing, grouping and re-grouping endlessly over eons of time, indestructible.  We mortals are collections of atoms and on death will revert to atoms.