That is why Peter was so dear to Jesus despite his flaws,for he would always admit his flaws,and turn from them,like king David who did some terrible things,but would quickly turn to the LORD and ask forgiveness.
Gal 2:11 But when Peter was come to Antioch, I withstood him to the face, because he was to be blamed.
Gal 2:12 For before that certain came from James, he did eat with the Gentiles: but when they were come, he withdrew and separated himself, fearing them which were of the circumcision.
Gal 2:13 And the other Jews dissembled likewise with him; insomuch that Barnabas also was carried away with their dissimulation.
Gal 2:14 But when I saw that they walked not uprightly according to the truth of the gospel, I said unto Peter before them all, If thou, being a Jew, livest after the manner of Gentiles, and not as do the Jews, why compellest thou the Gentiles to live as do the Jews?
Even after conversion Peter still had a problem,which Paul said he did not walk uprightly according to the truth of the Gospel.Peter is an example of how the Lord forgives,and even though a person can mess up quite often,can still find favor with the Lord,because of their persistent love for God,and the willingness to not give up,which Peter walked on water,but lost faith,and Jesus had to raise him up,and denied Jesus 3 times,and probably did things the Bible does not mention,but his attitude to keep trying,and not give up,found him favor and forgiveness with the Lord,and like David,Peter always would eventually turn from what he did.
And we know Peter is saved,without a shadow of a doubt,one hundred percent,can be proven,for his name is written in the New Jerusalem,and well as the other 11 apostles,and if Peter can mess up like he did,even after conversion,but still find forgiveness,and obtained salvation,than we can too despite our messing up,as long as we are persistent,not give up,have a zeal for the Lord,and have the same attitude as Peter.