I spent a long time working out what I believe and what I don't, once I trusted my reason again.
I don't think it is enough to work out all the things you don't believe in. To move forward, to make choices, to have a vision and a future, it pays to figure out what it is you do believe.
Recently my interest in religion was revived by an agnostic, Haidt. His is a utilitarian morality, not absolute. What is it that people care about, because of the way we are? (Haidt rates us as 90% chimp, 10% bee).
According to Haidt's model, religion does serve a purpose, even if it is built on myths. It unifies us to a higher cause, and people love it when we are united to a common cause. Case in point, a high school footbal game or the Battle of Britain.