happiness is a state of mind, if you're content and secure and feel loved and valued that is happiness, u have to expect things to go wrong sometimes like losing your purse or being late for a hospital appointment/ being ill or falling out with your best friend these things happen 20% of time, the other 80% is happiness. i think.
i believe it is more choice - you can have positive thoughts about negative situations and push things to go in that direction. some people are born that way, others are not
Happiness is very subjective and as said already comes from within .If you are healthy and can afford to eat then you should be happy but having friends and family around you is the most important thing in the world