Why I do what i don't want to do!

I was reading in Romans 7 this morning and although I knew the answer to the question I posed, it never hurts to have it slapped in my face from time to time. I do what I dont want to do because I was once controlled by sin. And without Christ as my release agent from sin, I would still be controlled by it. Does that mean that I do not sin, heck no it doesn't. Does it give me reason to sin, heck no it doesn't. Does it make sense that I sin, heck no it doesn't. But yet, I do it anyways. This is just another illustration as to why scripture seems so easy to understand and yet it is one of the most difficult things to comprehend.