On your feet
"Yea doubtless, and I count all things but loss for the excellency of the knowledge of Christ Jesus my Lord: for whom I have suffered the loss of all things, and do count them but dung, that I may win Christ, And be found in Him not having mine own righteousness..." (Philippians 3:9-10, emphasis mine)
It continues. Paul is speaking of the last vestiges of what Jesus came to kill in fallen humanity: This (now) outmoded notion that we can get to Heaven on our own.
Righteousness is a complex Greek word with several shades of connotation leading up to the main word dikaiosune. From "to show", to "right" and "justice", to "equitable", "innocent", "holy". All things which God requires for us to be in right standing. Which is another way of terming it.
But Isaiah says that "all our righteousnesses are as filthy rags" (Isaiah 64:6). Whatever are we to do? As an aside, God had Jeremiah take his "girdle" and, it says "go to Euphrates (a river in modern-day Iraq) and hide it there in a hole of the rock". Later on, "after many days" Jeremiah retrieved the garment and he says "behold...it was profitable for nothing." The event is recounted in Jeremiah, chapter thirteen.
Even today, among Christians and non, is this notion that if we live a moral life, we can acheive that ultimate prize: eternal life. Because that's what Jesus came to show, right? How to be a good person. And if we can just make it to the other side—we know this somehow—we'll be okay. Whatever the other side holds, as long as it's not hell, is fine with us. But this thinking is precluded by the fact that we know God is like a big parent in the sky who rewards accordingly. Maybe we think this because our parents treated us thusly and therefore imprinted this paradigm onto our minds. However you want to explain it away, you can't deny that God requires righteousness. And not just for Heaven, but for our day-in, day-out existence.
But then Isaiah had to go and slip that in there. Like the ultimate dichotomy.
Can you wrap your mind around the fact that God loves you? Unconditionally. Yes, He does require holiness because He is holy. But many of us (myself included) have no idea what true holiness looks like when so much of humanity rejects a pure standard of living. From inward truth and honesty, to outward selflessness in whatever form it might take. And God is a God of judgment. But first, He's a God of love. And He lived this love out through Jesus Christ. When Jesus offered Himself on the altar for our sin—our non-righteousness—that was good enough for God.
Anymore, our grasping for moral rectitude and probity is a waste of time with God. Because it's already been done. "It is finished" (John 19:30) said Jesus, right before He died. Now, the issue is not one of rightness or trying to acheive an (unreachable) standard, it's one of belief and trust. Obviously, this doesn't mean that you can go off and do whatever you want. Anyone reading into it that is mistranslating it into the irrational. Jesus acheived the impossible: He put us back into right-standing with God. Now it's up to us to renew our minds to God's selfless standard of living. The living out of what Jesus gives to us—our re-creation—begins with a continual belief in Jesus. "And having done all, to stand. Stand therefore..." (Ephesians 6:14)
In closing, the greatest of denominational rifts was borne from the misunderstanding of just what it is we do after accepting the sacrifice of Jesus. Honestly, common sense should shine through after understanding that it's sin that Jesus dealt with on the cross, and sins that we commit in lieu of righteousness. His sacrifice covers all of it.
"Jesus saith to him, He that is washed needeth not save to wash his feet, but is clean every whit: and ye are clean..." (John 13:10)
"But after that the kindness and love of God our Saviour toward man appeared, Not by works of righteousness which we have done, but according to His mercy He saved us, by the washing of regeneration, and the renewing of the Holy Ghost; which He shed on us abundantly through Jesus Christ our Saviour; That being justified by His grace, we should be made heirs according to the hope of eternal life. This is a faithful saying, and these things I will that thou affirm constantly, that they which have believed in God might be careful to maintain good works. These things are good and profitable unto men." And women! (Titus 3:5-8)