Optimists are born, not made, according to Nobel laureate Daniel Kahneman, who writes in Thinking, Fast and Slow:
An optimistic attitude is largely inherited, and it is part of a general disposition for well-being, which may also include a preference for seeing the bright side of everything. … A disposition for well-being is as heritable as height or intelligence.
Happiness, on the other hand, can be cultivated according to a very simple formula:
The easiest way to increase happiness is to control your use of time. Can you find more time to do the things you enjoy doing?
Enjoyment x Time = Happiness