Whatever happiness and peace that one knows in one's life is generally so fragile that it is always subservient to the external situation. So most of your lives go in trying to manage a perfect external situation which is just impossible to do. No human being is ever capable of creating a perfect external situation because the outside situation will never be hundred percent in your control, no matter how powerful a human being you are. So yoga focuses on the inner situation. If you can create a perfect inward situation, no matter what the external situation, you can be in perfect bliss and peace.