The world will tell you that the answer to all of your sadness and sorrow is to be found in an improved "self-esteem". The "church" will often tell you that to doubt, to question, to be depressed, to be too fixated on your own short-comings shows a lack of faith and/or evidence of a false conversion. Instead of ministering to the wounded, they pour their self-righteous salt into the open wounds of a beloved. Listen to what a godly man; a man who was so saturated by a deep love for Christ, a brain and heart so filled with the Word of God that it flowed freely from his heart to his pen--listen to how he describes a "sincere" believer:
Sincere believers are often cast down by the realization of how far, far short they come to measuring up to the standard which Christ has set before them. According to the yearnings of the new nature--you have sincerely endeavored to follow Christ's example, but being weak in grace and meeting with much opposition from the flesh and temptations from the Devil--you have been frequently turned aside from the holy purposes and designs of your honest hearts--to the great grief and discouragement of your souls.
You can heartily say with David, "O that my ways were directed to keep Your statutes!" (Psalm 119:5), and you have tried hard and long to follow after exact holiness, "if by any means you might attain unto it." But your efforts have been repeatedly thwarted, your aspirations dashed, and you have to cry out, "O wretched man that I am! Who will free me from this life that is dominated by sin!" (Romans 7:24)
First, let us assure the genuinely exercised soul, that such defects in obedience do not invalidate your justification, or in any way affect your acceptance with, and standing before God. Your justification is not built upon your obedience--but upon Christ's. However imperfect you are in yourself, you are "complete in Him" (Col. 2:10). Woe had it been to Abraham, Moses, David, and Paul--if their justification had depended upon their own holiness and good works. Let not, then, your sad failures dampen your joy in Christ--but rather be increasingly thankful for His robe of righteousness, which hides your filthy rags!
Second, your heart-anguish over your unlikeness to Christ, evidences that you have a sincere acquaintance with the evil of your heart, a deep loathing of sin, and truly love God. The most eminent saints have made the bitterest lamentation on this account, "My sins have flooded over my head; they are a burden too heavy for me to bear. My wounds are foul and festering because of my foolishness!" (Psalm 38:4-5)
Third, the Holy Spirit makes an excellent use of your infirmities, and turns your failures unto spiritual advantages. By those very defects--He humbles you, subdues your self-righteousness, causes you to appreciate more deeply the riches of free grace, and to place a higher value upon the precious blood of the Lamb. By your many falls--He makes you to long more ardently for Heaven--and gradually reconciles you to the prospect of death. The more a holy soul is buffeted by sin and Satan--the more sincerely will he cry out, "Oh that I had wings like a dove! for then would I fly away, and be at rest!" (Psalm 55:6). "O the blessed chemistry of Heaven, to extract such mercies--out of such miseries!" (John Flavel), to make sweet flowers--spring up out of such bitter roots!
Fourth, your bewailed infirmities do not break the bond of the Everlasting Covenant! That holds firm, notwithstanding your many defects and corruptions. "Iniquities prevail against me" said David--yet in the same breath he added, "You shall purge them away!" (Psalm 65:3)
Fifth, though the defects of your obedience are grievous to God--yet your deep sorrows for them are well-pleasing in His sight, "The sacrifices of God are a broken spirit--a broken and a contrite heart, O God, You will not despise!" (Psalm 51:17)
Sixth, your very grief is a conformity to Christ--for when here, He was "the Man of sorrows." If He suffered because of our sins--shall we not be made to weep over them?
Seventh, "Though God has left many defects to humble you--yet He has given many things to comfort you. This is a comfort--that your sins are not your delight as once they were--but your shame and sorrow! This is a comfort--that your case is not singular, but more or less the same complaints and sorrows are found in all gracious souls in the world!" (John Flavel)