Ladies, when your husband tells you you're beautiful, he's not lying, even if you think he is. In his eyes, you are beautiful. Why is that so hard to believe? Because you see yourself differently from how he sees you. Marriage means learning to believe your husband and to see yourself as he does.
That's the ideal. Sure, there are wicked husbands whose eyes make comparisons and haughty wives who consider themselves more highly than they ought. But the ideal comes from the Ideal Marriage, between Christ and His Bride, the Church.
In His eyes, there is none more beautiful. He should know, after all, since He has made her peerless in beauty, removing the filth of her sinfulness and clothing her in the beauty of His righteousness.
There's little practical difference between Oprah's positive thinking and the Word-Faith movement, except one claims to take the majority of its inspiration from Scripture. Both exhort you to get your thinking in order so that good things will follow. And both are wrong (and, neither is contained in Scripture).
But what you think does matter. Your thinking doesn't determine reality, but reality determines your thinking.
Here's the reality: those who are "in Christ" are free from sin and its condemnation. God knows this. He declares it, and so it is. This is justification, being made righteous before God.
Sanctification is learning to believe what God knows to be true about you. From your perspective, though, you don't seem that sinless. You seem to embody what St. Paul describes in Romans 7, the life-long conflict between your old sinful self and your new sin-free self. But God who sees and knows all things, and who has declared you righteous for the sake of Jesus, doesn't see it like you see it.
Who's right? God is. And yet, for the time being, so are you. And you still struggle against sin. The problem is that the reality God knows, where your sins are completely taken away and given to Jesus and His righteousness completely imparted to you, is hidden to your eyes.
The Christian life, growing in grace and holiness, is not a matter of getting better. It's a matter of learning to believe about yourself what God knows and has declared to be true. In Jesus, you are sinless. You have no sins; they belong to Him. He is, after all, the Lamb of God who takes away the sins of the world.