I consider everything as a loss because of the supreme good of knowing Christ Jesus my Lord. For his sake I have accepted the loss of all things and consider them so much rubbish, that I may gain Christ and be found in him to know him and the power of his resurrection and the sharing of his sufferings by being conformed to his death. (Phillippians 3:8-9a, 10)
And in this is nearly all the doctrine of the great Carmelite mystics. "I consider everything as a loss because of the supreme good of knowing Christ Jesus," that is, nothing in the world is as worthy of our attention as Jesus Christ--thus every moment spent outside of Jesus Christ is a loss--even if it is a participation in very good things.
"For his sake I have accepted the loss of all things and consider them so much rubbish. . ." Because of His preeminent place in the universe everything else is tarnished and weary. Paul at one time was a wealthy citizen of Jerusalem, well known, apparently well connected. But when he became a Christian he lost all of this. And the loss was as nothing--as a mere casting off of outer soiled rags. In fact, other translations have much stronger words than merely rubbish. But Paul is not proposing here some sort of dualism. Everything is brought into focus by the central point of attention--Christ Jesus.
". . .that I may gain Christ and be found in him to know him and the power of his resurrection . . ." There is purpose here in casting off outer things. We do not rid ourselves of them because they are evil. We rid ourselves of them because they are less worthy of our attention. They are distraction on the path to unity with God. Through casting off these lesser goods we make more room for Jesus Christ--we are "found in him" or claim our true identity as a child of God. This is our ultimate and most important identity. In finding Him, we come to know the power of His resurrection--that is the redemptive, saving power of Grace. But more importantly, we come to know it in a way that cannot be merely intellectual. This is heart-knowledge. We know Jesus Christ intimately as indwelling and ever present with us. We commune with Him and we share every aspect of our life with Him.
". . .and the sharing of his sufferings by being conformed to his death." And a bit of speculation here--perhaps Paul is obliquely referring to a "dark night." Paul certainly shared Christ's sufferings on a material plane, but if all of this is as dross and as rubbish then it would hardly matter if he knew the constant presence of Christ. The only suffering that would matter is that feeling of abandonment, that moment on the cross when Jesus cried out "Eloi, Eloi, lama sabachthani." That is the true suffering. Feeling abandoned at the shallow surface of emotion, but knowing in the depths of the heart God is there with us and He suffers again in our suffering. One metaphor often used for the dark night is that of the surgeon performing an operation to remove all that withholds us from communion with God. But this is the Divine surgeon, all that we feel, He feels. He felt it at that moment on the Cross and He feels it throughout eternity. And yet, nevertheless, the step is necessary if we are to have health and to be restored to life in Him. We suffer it either in this realm or in the world to come as we undergo purgation that will ultimately allow us to enter into the heavenly abode.