When the bible talks about how everyone sins and that there is no one is righteous, it refers to the depravity of people. We can not, not sin (I know, double negative) because of our corrupt nature, meaning we cannot come to God and attain a relationship with Him all on our own. It is not in our power and is impossible because of the inclination of our wicked heart. As Mark Driscoll says, We are sinners by nature and choice.
But then on the other hand, when the bible speaks that we need to pursue righteousness and carry our cross and put our sins to death, it’s talking about how the Holy Spirit that we receive and it enables us, and our new nature that comes from Jesus Christ and we begin to desire holiness and righteousness, and begin to passionately hate sin.
So when looking at two different verses not as contradicting, but as different perspectives. Both are true in their own context.
as it is written: “None is righteous, no, not one; no one understands; no one seeks for God. All have turned aside; together they have become worthless; no one does good, not even one.” (Romans 3:10-12)
And whoever does not take his cross and follow me is not worthy of me. (Matthew 10:38)