"...the trouble is with me, for I am all too human, a slave to sin. I don't really understand myself, for I want to do what is right, but I don't do it. Instead I do what I hate...I know that nothing good lives in me, that is, in my sinful nature. I want to do what is right, but I can't. I want to do what is good, but I don't. I don't want to do what is wrong, but I do it anyway...I have discovered this principle of life - that when I want to do what is right, I inevitably do what is wrong...Oh, what a miserable person I am! Who will free me from this life that is dominated by sin and death? Thank God! The answer is in Jesus Christ our Lord..." ~ Romans 7 v 14-25 
I can definitely relate to Paul's struggles here. I often find the same thoughts going round and round my head: I know what I do is wrong, but I carry on doing it anyway. I feel at the moment that God is really showing me how much of a wretched sinner I am. This might seem like an unloving thing for God to do but I am starting to realise how infinitely important it is that He is doing this for me. How can I understand fully the huge-ness of the sacrifice that Jesus made for me without recognising the full extent of my sin - my need for him? Yes, it's important not to dwell on our faults, Jesus has freed us from our sin and he "no longer counts people's sins against them" (2 Corinthians 5 v 19) - but, it is important to understand how small we are to understand God's greatness and to realise his truly amazing love for us! Mark 2 v 17 says "Healthy people don't need a doctor - sick people do. I have come to call not those who think they are righteous, but those who know they are sinners." I was in massive need of a Saviour - and I received Him! 
A friend sent me a sermon from 1844 spoken by a man called Charles Finney called "Blessed are the poor in spirit". Finney speaks so honestly and beautifully about the struggles with sin. Here is the last paragraph, which encouraged me so much:
"These seasons of spiritual poverty are indispensable to holding on to Christ. See a young convert--young converts know little of themselves or of Christ. They run well for a time, but they must be taught more of Christ, and this they can learn only by learning more of themselves. Well, Christ begins the work in a soul. The convert was all joy, but his countenance falls. Poor child! do not scold him. He is sad; he dares hardly indulge a hope. What is the matter? He desponds. You encourage him to trust in Christ and rejoice in him. But no, that will not serve the turn, that does not remove the load. Christ has undertaken a work with him--has set about revealing him to himself, and the work will cost the poor soul many prayers, and tears, and groans, and searchings and loathings of heart. He prayed before for sanctification and he is astonished out of measure. He receives any thing in the world but sanctification. He prayed for the Baptism of the Holy Ghost, and he verily expected some beatific sight. He thought he should see the heavens opened as Stephen did. But instead of this, what a state! He seems given over to the tender mercies of sin. Every appetite and lust is clamorous as a fiend; his passions get the mastery; he frets, and grieves, and vexes himself, and repents and sins again; he is shocked, ashamed of himself, afraid to look up, is ashamed and confounded. Poor thing! he prayed to be sanctified, and he expected Christ would smile right through the darkness, and light up his soul with unutterable joy. But no! it is all confusion and darkness. He is stumbling, and sliding, and floundering, and plunging headlong into the mire, till his own clothes abhor him, and he is brought to cry--"Lord, O Lord, have mercy on me!" He expected--O what a fairy land! and he finds--what a desert--barren, dark, full of traps, and gins, and pitfalls; as it were the very earth conspiring with all things else, to ruin him. Child, be not disheartened; Christ is answering your prayer. Cold professors may discourage you, but be not discouraged; you may weep and groan, but you are going through a necessary process. To know Christ, you must know yourself; to have Christ come in, you must be emptied of yourself. How will he so this for you? If you would but let go of self--if you would but believe all that God says of you, and renounce yourself at first and at once, you might be spared many a fall; but you will not, you will believe only upon experience, and hence that experience Christ makes sure that you shall have to the full. And now, mark: whoever expects to be sanctified without a full and clear and heart-sickening revelation of his own loathsomeness, without being first shown how much he needs it, is very much mistaken. Till you have learned that, nothing you can do can avail aught; you are not prepared to receive Christ as he is offered in the gospel."
