Not many Christians think of themselves as unbelievers. After all, we normally use the term to describe people who aren’t Christians at all. Most of us can happily sign up to the creeds of our church. But our problems rarely arise from a lack of belief in a confessional or theoretical sense, though this may be the case. More often they arise from functional or practical disbelief. The problems lie in the gap between what we believe in theory and what we believe in practice.
--Tim Chester, You Can Change: God's Transforming Power for Our Sinful Behaviour and Negative Emotions (IVP 2010), 82; sample chapter here