Ajahn Chah

There is truly nothing there.

It doesn't arise with conditioned things and it doesn't die with them.

When the mind encounters something good, it doesn't change to become good

When the mind encounters something bad, it doesn't become bad as well.

That's how it is when there is clear insight into one's nature.

There is understanding that this is essentially a substanceless state of affairs.

the Buddha's insight saw it all as impermanent, unsatisfactory and not-self.

He wants us to fully comprehend it in the same way.

The knowing, then, knows in accordance with truth.

When it knows happiness or sorrow, it remains unmoved,

The emotion of happiness is a form of birth.

The tendency to become sad is a form of death.

When there's death, there is birth.

And what is born has to die.

That which arises and passes away is caught in this unremitting cycle of becoming.

Once the meditators mind comes to this state of understanding, no doubt remains about whether there is further becoming and rebirth.

The Buddha comprehensively investigated conditioned phenomena and so was able to let it all go.

The five khandhas were let go of and the knowing carried on merely as an impartial observer of the process.

If he experienced something positive

he didn't become positive along with it.