The main point is that people should be the master of emotions.
Problem: In life, often we feel overwhelmed by emotions. For example, when we feel happy about others' praise, it often means that we will also feel sad at hate speech by others. There can also be other more devastating emotions that can destroy our mental health, or make our life difficult.
(Disclaimer: I haven't proved the theories below. They are more like a summary of what are commonly said, and some preliminary speculation. Do not immediately use them in action if they don't make sense to you.)
Solution: The core reason that buddhism identifies is that people are attached to objective things. The world changes according to certain causal mechanisms (which can be purely objective), but people tend to link such objective phenomena with subjective feelings. If we can step back and practice calmness (through zen meditation, for example), then we can stay resilient no matter what happens in life. Also at critical times, we can stay calm and concentrated, focusing on the objectively right things to do, but not surrender to emotions.
The reason for most people to link objective things with subjective feelings is that we "crave" for things. That is why buddhism encourage people to practice "detachment", i.e., stop craving for external things, but focus on inner calmness. Specifically, things belong to the physical world, but are not ours; nor is the perceived "self" ours. I think this tends to return to the question of adaptation -- the less a person requires from external world (e.g., people can find/make substitutions but not deeply attached to a fixed thing), the more adaptable the person is to all kinds of situations, e.g., when there are fires/wars/disasters when people have to leave all properties behind. We live because our inner spirit exists, not limited by external belongings.
Key points in the book: - 菩提自性。本来清净。但用此心。直了成佛。Translation: The enlightenment is nowhere but in our pure heart. Once we truly get to know ourselves, we become the enlightened. - 菩提本无树 明镜亦非台 本来无一物 何处惹尘埃。 - 何名禅定。外离相为禅。内不乱为定。We can achieve the Zen Buddhism by detachment from the external phases, and obtainment of inner calmness.
Some nice quotes: - 惠能向别驾言。欲学无上菩提。不可轻于初学。下下人有上上智。上上人有没意智。若轻人。即有无量无边罪。 - How to do it: 但持金刚经。即自见性。直了成佛。What is the effect: 无上菩提。须得言下识自本心。见自本性。不生不灭。于一切时中。念念自见。万法无滞。一真一切真。万境自如如。如如之心。即是真实。若如是见。即是无上菩提之自性也。 - 求道之人。为法忘躯。当如是乎。 - 一切万法不离自性。遂启祖言。何期自性本自清净。何期自性本不生灭。何期自性本自具足。何期自性本无动摇。何期自性能生万法。 - 时有风吹幡动。一僧曰风动。一僧曰幡动。议论不已。惠能进曰。不是风动。不是幡动。仁者心动。 - 佛言。善根有二。一者常。二者无常。佛性非常非无常。是故不断。名为不二。一者善。二者不善。佛性非善非不善。是名不二。蕴之与界。凡夫见二。智者了达。其性无二。无二之性。即是佛性。=> This sounds like the true enlightenment will be converged and not inconsistent (非无常). Plus, it is consistent but not simply constant (非常). - 菩提般若之智。世人本自有之。只缘心迷。不能自悟。须假大善知识。示导见性。 - 万法在诸人性中。若见一切人恶之与善。尽皆不取不舍。亦不染着。心如虚空。名之为大。故曰摩诃。=> When one sees all the good and bad sides of the human nature, but is still not attached/immersed in them, then this is the 摩诃 in heart. Basically we need to understand human nature, and how society and nature work, while still keeping the pureness in our heart. - 一切即一。一即一切。去来自由。心体无滞。即是般若。=> Freedom from material and emotions is 般若 wisdom. - 善知识。内外不住。去来自由。能除执心。通达无碍。能修此行。与般若经本无差别。=> We don't necessarily need to be attached to text in books, because the real enlightenment is within us. - 随所住处恒安乐。 - 汝观自本心。莫着外法相。法无四乘。人心自有等差。见闻转诵是小乘。悟法解义是中乘。依法修行是大乘。万法尽通。万法俱备。一切不染。离诸法相。一无所得。名最上乘。
Some critical thinking: - Buddhism suggests that we should use calmness to replace all emotions. But are emotions bad? Is such criticism of emotions too extreme: 人我是须弥。 贪欲是海水。烦恼是波浪。毒害是恶龙。虚妄是鬼神。尘劳是鱼鳖。贪瞋是地狱。愚痴是畜生。