no, not willfully sin, but if one do sin, scripture, 1 John 2:1 "My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:"
the point is as our brother Paul by the Holy Ghost points out, NOT to sin, but, Philippians 3:13 "Brethren, I count not myself to have apprehended: but this one thing I do, forgetting those things which are behind, and reaching forth unto those things which are before,"Philippians 3:14 "I press toward the mark for the prize of the high calling of God in Christ Jesus."
and the apostle Peter noted, 1 Peter 2:2 "As newborn babes, desire the sincere milk of the word, that ye may grow thereby:"
I have never seen a new born NOT make a mistake, as you said this is a process, we do better when we learn to do better.
PICJAG
101G The "Spiritual Saboteur"
Correct, no willful sin. And yes, new born babes crawl before they learn to walk.
1 John 2
[3] And hereby we do know that we know him, if we keep his commandments.
[4] He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.