> think positive, be happy!
This is correct. It is hard to do all the time. But it's a better way to live. Happiness / unhappiness is a choice (depression other mental illnessesses and additions are conditions to be treated, out of scope, it is not "unhappiness").
Think of it this way.
You can be poor, have kids to feed, homeless, whatever. And unhappy.
Or, can be poor, have kids to feed, homeless, whatever. And happy.
You can wallow in self-pity, blame yourself (or others, society) for your situation, be cynical and pessimistic. Or, be happy, see the positives, be optimistic, try and improve your situation.