Here’s how Tim Keller used to explain our sin problem:

Imagine your present self looking at your past self, say 10 years ago. Your present self thinks your past self was a fool. Your present self looks back and says, “Back then, I needed guidance I didn't understand. I was so naive. I was so silly. I was immature. I behaved badly.” So, your present self always thinks of your past self as a jerk. Well, the problem is that your future self will think of your present self as a jerk 10 years from now. You'll look back now and say, “Back then, I thought I needed guidance. I thought I understood, but I was such a fool.”

Here's the blunt bad news about our condition: You're always a jerk, but you always think you're just getting over it. We always think that we've just arrived. It's what you thought when you were 15. Then, then you looked back at your 12-year-old self and said, “Now I've arrived. Boy, what a dummy I was when I was 12. I'm ready for the world now.” By the time you're 20, you say that 15-year-old self was so ignorant and flawed and sinful. But you see here’s the point: you’re always ignorant and flawed and sinful, but you continually think you're just getting over it. Sin is deeper in us than we ever imagined.