Dukha literally means "contracted space". Some traditions hold that dukha is a fundamental quality of existence. I don't subscribe to this view. Anyone with any sensitivity who has spent any amount of time in nature understands this on a deep level. One definition used for dukha oftentimes is "suffering". Is suffering a quality of existence itself? I think it is important to look deeper. If you really look, existence contains within it hardship. Some have it easier than others. But is this the same as suffering? Is this the same as contracted space? No. Hardship and suffering are different. We have all seen in our life how sometimes one has the most intense hardships and yet hardly suffers, while others living in the lap of luxury suffer the worst hells of their own imaginings. Hardship may be a quality of existence but suffering is not. Our natural world is filled with space, openness.
Dukha is a product of our own mind. Illusions take place there, for bad or good. The natural world is as it is, natural, open, spacious, vast. To enter this world we have to let go of that which contracts us. This is true Khecari, that powerful mudra which means "to go or to move in space".
Working with the nadis, we see where we are contracted, where we cling. What does it mean to let go into space? Does it mean we let go through external action, relinquishing our physical world? No. The relinquishment takes place on a deep mental, deep bodily level. We actually let go into the truth that is staring right at us. We are living and breathing right now in that space.
The world of sukha or "open space" is a vast one. Infinite potential. Bliss of our truth. And what is that truth? That everything is as it is. Things as they are are wondrous, beautiful, and reflect constantly to us the Light of who we are. Matter IS Spirit. Spirit IS Matter. There is no split. There is no contraction. Dukha is only like a dream.