I am reading 'Spiritual Depression Its Causes and Cure' by Martyn Lloyd-Jones and have found a most profound passage that I thought worthy of sharing. The book has been excellently written and is difficult to put down. The passage I am quoting is concerning sin and whether or not you know that you are a sinner.
"Here is the test for you and me: Are you loving God with all your being? If you are not, you are a sinner. That is the test. 'All have sinned and come short of the glory of God.' God has made us and He has made us for Himself. He made man for His own glory and He intended man to live entirely for Him. Man was to be His representative, and was to dwell in communion with Him. He was to be the lord of the universe, he was to glorify God. As it is put in the Shorter Catechism: 'The chief end of man is to glorify God and to enjoy Him forever', and if you are not doing so you are a sinner of the deepest dye, whether you know it and feel it or not....So the question is: Do you know God? I am not asking if you believe in God, or if you believe certain things about Him. To be a Christian is to have eternal life, and as our Lord says in John 17:3: 'This is life eternal to know Thee the only true God, and Jesus Christ, whom Thou hast sent'. So the test we apply to ourselves is that. Not, 'Have I done this or that?' My test is a positive one: 'Do I know God? Is Jesus Christ real to me?' I am not asking whether you know things about Him but do you know God, are you enjoying God, is God the centre of your life, the soul of your being, the source of you greatest joy? He is meant to be."