From the perspective of mind-essence, the interruptions of thoughts are like clouds in the sky. The empty essence itself is like the space of the sky. Our cognizance is like sunshine. The sky itself never changes whether it’s sunny or cloudy. Similarly, when you realize the awakened state of the buddhas, all clouldlike thoughts have vanished. But the qualities of wisdom, meaning original wakefulness, are fully developed, fully present, even now, when thoughts are present. We need to train in slowly growing more and more used to the recognition of mind-essence. This will dissolve our negative karma and disturbing emotions. In this recognition it is impossible to be tainted by karma and emotions, just like midair cannot be painted.
I would like to give you a famous quote from the Hevajra Tantra:
“All sentient beings are buddhas,
But they are covered by temporary obscurations.”
This temporary obscuration is our own thinking. If we didn’t already have the buddha nature, meaning a nature that is identical to that of all awakened ones, then no matter how much we tried we would never be enlightened. The Buddha used the example of churning milk into butter. Sentient beings contain within themselves the butter-yielding milk, in the sense of this basic material of enlightenment. It is not like we are water — you could churn water for a billion years and still never get butter from it. All sentient beings have the essence of buddhahood within themselves. But if you ignore this most precious essence inside yourself, you will continue spinning around in the three painful realms of samsara.
~ tulku urgyen rinpoche