The Al-Anon version of happiness (Al-Anon is for friends and family of alcoholics) is gratitude. Cultivate gratitude and you will find happiness.
Oddly, I have found changing my diet to make happiness more readily available. And others I know say the same thing. It's astonishing, really. Happiness isn't that much work and yeah, it really doesn't depend on outside circumstances.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 180 x 2. Current Deadlift: 230 x 2