So it is with us. Our problem is what we are, nor how hard we try. The Bible says what we ARE is unrighteous. No matter how we try, we cannot change what we ARE. For a salmon to be a bird it would have to be reborn as a bird. So for us to be righteous we must be born again as righteous. Without rebirth we are all unrighteous. It is not surprising then that Jesus said, "You must be born again." Remember the word "unrighteous," and be born again by believing in Jesus, The righteous.
Romans 3:9-10 "We have demonstrated that both Jews and Gentiles are ALL UNDER (the dominion, power and authority of) sin; as it is written, there are not righteous, no not one." (parenthesis added)