Gratitude was always part of her happiness routine, but when Sienna Saint-Cyr started practising yoga for gratitude, she found a new lightness, peace and energy within.    Gratitude – and gratitude yoga – is a catalyst for happiness. When we're grateful for what we have, we stop focusing on the things we lack. But why exactly? Gratitude expert Robert Emmons shares that when people help one another, they feel happier. The actions they take release the feel-good hormone oxytocin. It's th