Romans 11:32   God has bound all men over to disobedience so that he may have mercy on them all.  

We wouldn't need mercy if we were righteous. Whether it is nations and people groups, or individuals, we all have a common affliction and a common need for mercy and forgiveness. I think it is only when we try and fail, when we stumble and fall, do we recognize our true condition and perceive our need for God. Perhaps that's why he gives us so much freedom. 

I like to characterize myself as an  old sinner  saved by grace. None of us are getting saved any other way! I even call the album I am working on " Songs from a Sinner ". It's what I was (big time), and without Jesus, it is what I am. Without him, it's all I can ever be - o nly in Christ,  do I have any claim to righteousness! 

Sometimes, I run into the self-righteous sort, who say things like " what a name for an album - I thought you were supposed to be a Christian - why do you call yourself a sinner ?" However, like Paul, I must declare myself " the chief of sinners " (and do away with any pretense). Only in Christ, am I anything but a sinner. I must get out of bed each day and  crucify  the old man. If I allow myself to live, instead of Christ living in me, I will inevitably sin, despite all the theology I have studied or how valiantly I strive to apply it. Romans 6:6; Ephesians 2:15; 4:22-24; and Colossians 3:9-11 . 

Some sincere Christians deny that believers possess a sin nature which must be warred against and overcome. Often, it is because they have misunderstood Wesley's doctrine of " entire sanctification " and take it to extremes that he did not intend. Yes, we are to press forward in Christian maturity and perfection of character but with the knowledge that until glorification we still have a sin nature to contend with, though it should no longer dominate us.

Only let it be remembered, that the heart, even of a believer, is not wholly purified when he is justified. Sin is then overcome, but it is not rooted out; it is conquered, but not destroyed. Experience shows him, First, that the roots of sin, self-will, pride, and idolatry, remain still in his heart. But as long as he continues to watch and pray, none of them can prevail against him. Experience teaches him, Secondly, that sin (generally pride or self-will) cleaves to his best actions: So that, even with regard to these, he finds an absolute necessity for the blood of atonement.  The Sermons of John Wesley - Sermon 123 The Deceitfulness Of The Human Heart

In fact, Paul says his righteousness as a Pharisee (blameless under the law), was rubbish compared to the righteousness that comes through faith in Christ. (Philippians 3:4-9). You would be hard pressed to find anyone who was more zealous, or better trained, but self-effort didn't result in righteousness for Paul! He came to realize that he was a sinner, who needed salvation by grace, through faith. 

Romans 3 21-24   ...For there is no distinction among people since all have sinned and  continue  to fall short of God's glory. By his grace, they are justified freely through the redemption that is in the Messiah Jesus...  

You see, only Christ's spotless robe of righteousness is acceptable at the marriage supper of the Lamb. Those who think their own righteousness (filthy rags by comparison) are worthy, are in for a shock (Matt. 22:13). We must allow Christ to take away our filthy garments, and be covered in HIS robe. A merciful covering for our sin and shame - a gift we cannot earn and don't deserve. That's grace - it's free, but it's only available to sinners! 

In the story of the Pharisee and the publican, only one went home justified, the one who confessed he was a sinner. The self-righteous, the hypocrites, the presumptuous, do not receive the imparted, or imputed righteousness of Christ. You must come to the place where you realize your true condition before you will perceive your need for a Savior and throw yourself on God's mercy.

That's not to say that we need not repent, or need not war against and overcome sin. He will empower and motivate us to do so, as long as we choose to abide in him. Sin will no longer be our master, we are called to walk uprightly, not in the habitual sin of our former lives. However, if we stumble in our walk, we have an advocate. Grace and mercy for our shortcomings  is  available.

1 John 2:1  My dear children, I write this to you so that you will not sin. But if anybody does sin, we have an advocate with the Father--Jesus Christ, the Righteous One.  

Proverbs 28:13   He that covereth his sins shall not prosper: but whoso confesseth and forsaketh them shall have mercy.  

If you have been confused by the conflicting messages coming from different " camps " within Christianity regarding sin and salvation, here is a little deeper study along these lines Romans 7 - The Divided Man