True Happiness

Anuruddha's story really impressed me. First of all, the crudeness of it; poor Anuruddha getting blind after his efforts of not falling asleep again. But then, this idea of Buddha Shakiamuni as the person more actively looking for happiness in the world helped me to make more vivid the importance of our quest for true happiness. When one thinks about it, it is a concept strange to Western religious thought. We tend to view spirituality just as renunciation, and not as a quest for happiness. Happiness will come after you die, and the world is just a valley of tears.
As Aoyama wisely presents in this week's text, happiness is a state of mind, not the result of our external circumstances, and we need to learn acceptance on what there is, and what we are.
Logic and taoist philosopher Raymond Smullyan once wrote that "the Tao is about doing what you like; and zen is about liking what you do". So we are always within the same paradox: should I accept what is there? Or should I try to change it? Do what I like? Or liking what I must do?
So here is the open question, a question that comes to me quite often:

How do you decide whether to accept things as they are or trying to change them? What is your main criterion?