Happiness comes from within. No one can teach you how to be it, nor can they dissuade one from sinking into self-pity. It is up to the individual to determine they will be happy.
There are plenty of challenges for those with a sunny disposition. The depressed will test you with their pessimism. The despairing will vex you with their cynicism.
Just because you are happy, it does not mean everything will work out. It does not prevent bad things from happening. It means no matter how bad it gets you will not let it get you down.
The wicked can never be truly happy. There is nothing within to be satisfied with. Their every day is spent hammering nails into what will eventually become their coffin.
Strive to make things better for yourself and others. Contentment should always be a temporary state. When one obstacle has been overcome, set your sights on the next.
Misery within cannot be indefinitely contained. Eventually, it will spill forth when you least expect it. Happiness is too good not to share, so spread it around both far and wide.