I've been taught again that the atitude of having zero expectation is extremely useful in preventing disappointment. It works rather simply... if you have no expectation, you will have no disappointment. If you have high expectations, and people fail to meet ur expectation, you'll inevitably be upset. When you have no expectations, anything that turns out good is a bonus and the surprise will often make you happy! :)
Perhaps of a higher 境界 is to have expectations and yet not let the unmatching outcome affect you. Who knows which is better?
