Your "happy" may not be my "happy."

That is why you should focus on your own happiness and wellbeing, and let other people do the things they need to do in order to feel good. :)

Yes

Definitely! Look at Maslows 'hierarchy of needs theory' - depending on what you have, your needs and with these your definition of Happiness changes. If your hungry and cold, a bowl of hot soup will make you happy, if you are an successful entrepreneur it will be very very different. Happiness is deeply personal - only YOU know what makes YOU happy, and it's nobody else business...