Progress comes down to one thing: action.
Happiness comes down to one thing: progress.
When we are moving forward and growing, there is a feeling of reward from expansion of the self. It is from this feeling of becoming the best version of yourself which the soul attains true happiness; a feeling of certainty and peace.
If one ever finds themselves in a state of stillness, take action in a small way, and allow it to evolve into something greater.