Your 'self' wishes this world to be X, yet this world is not X. The mental state that may result to the 'self' from this disparity is Dukkha.
[And] how do we weaken the grip of the "self" which is that source of the gap of judgments and views between "how things are" and "how the self selfishly wishes they would be" ?
Why, "Just Sit", dropping all thought of "good" and "bad" , "right" , "wrong" , "just" and "unjust" , experiencing a world that just is-what-it-is without gap or separation. It goes-the-way-it-goes, even if that way is not the way we personally might desire. Letting aside both "cruel" and "gentle" , "ugly" and "kind" , we no longer resist, do not judge, and embrace it all ... even the most terrible.
Then the "self" loses its fuel, is put out of a job ... Dukkha is extinguished in a flash.