The Sutra of Perfect Enlightenment is interesting for many reasons. One is because everything one needs to wake up is present in the first two chapters. These basically fall under the category of Sudden Enlightenment. The rest of the Sutra can sort of be categorized as Gradual Cultivation. Though really it is more like painting legs on a snake. It is almost as if each subsequent chapter could be started with "So you didn't quite get the previous chapters, so..."
That is not to put subsequent chapters in a negative light! How many people read the first chapter, get it, wake up and don't need any more reading? This is only anecdotal evidence - I haven't heard of any. In fact, what happens is upon different readings of the Sutra, different chapters hit home.
What is Sudden Enlightenment? Have you ever had a moment of before thought mind? Zen Master Seung Sahn used to ask questions like: You, me, this wall, same or different? Have you ever had a moment where, without thinking, that made sense? The Zen cannon is full of stories with the final paragraph being something about enlightenment. E.g. Wonhyo's enlightenment story:
He was super thirsty in the middle of the night, felt around with his hands, found some water and drank it - how refreshing. In the morning he woke up and saw it was the skull of a dead animal and very gross. He threw up. Upon seeing the power of the mind he was enlightened.Of course, we have to take these stories with a grain of salt. Is it true as written? I've read several versions of the story, so most likely no. Did something like that happen? Possibly. Anyway, there are many stories like this and maybe you even have your own.
So maybe something is attained. There are a couple of issues here. The first is that experiences pass fast. Trying to hold on to them is like trying to hold water in your hands. The second is the mind instantly starts to create a story about what happened. After a time, is the experience remembered? Or the story about it? Again, something is attained. Maybe we begin to see we are all one. (Please don't make this into a concept - it is easy to chew this up with the mind.)
So maybe we see the folly of our selfish ways. Even dropping the mind's idea of a separate self. Wonderful! Do our actions change all at once? Are we suddenly calm, peaceful, considerate drivers? Are we happy for others when they get what we want? These are broad examples, it could be more subtle. Do we give freely of our time? Gossip about others? Listen to the thoughts going on and continue to believe them? Think that we have some spiritual weight now?
Maybe. Maybe not. Instead of focusing on any experience or event. We return to this moment. What is in front of us? Can we help someone? We return to the practice. We may have fundamentally changed. Yet, more work is likely necessary. Be it more practice, changing our actions, breaking our habits, breaking our addiction to the mind. We must cultivate our experience.
