Why is it that we sin so much?

We all know what sin is, yet we do it on a daily basis that it's become habit. I keep sinning and I don't know how to stop. I keep falling down, even when what I am about to do is sin yet I keep engaging in such activities. Why is it that sin is so.. fun? I can't explain it better, men want to sin so men sin. I have so much guilt and I spend hours in prayer asking for forgiveness. I just can't accept that I keep doing it knowing what Jesus did for me. How is it that we learn to stop sinning? The bible states we ALL fall short of the glory of God, yet I feel that no matter what I do I always will sin and there is nothing I can do do ever change. I am a sinner and I know it, it's time for me to change yet I can't. I always keep falling down. Why? It's not on just some issue, it ranges over so much of what the bible tells us not to do. Every sin is equally bad, at least that's what I've been told. What can I do?