p105 Always rely upon a happy mind alone. The measurement of having trained our mind is that we are always calm and happy

Always rely upon a happy mind alone. The measurement of having trained our mind is that we are always calm and happy. Before we have trained our mind, it changes according to our circumstances. When times are good, we are happy, but when they change for the worse, we become unhappy. Our mind is so unstable that it can change in an instant, one moment happy and excited and the next downcast and despondent. A controlled mind will remain happy and calm no matter what the conditions. Some scholars and meditators have called training the mind "the city that is the source of happiness".