An atheist shouldn't disbelieve in a second life, they should simply view the probability - based on current evidence - of such a thing existing as being extremely small. A seasoned atheist would also not view one or two personal experiences (in seclusion) of astral projection as conclusive proof, due to the many unknown factors in the experience, how it occurred and our current knowledge of mind and brain. It's perfectly possible to project and be an atheist, it simply means you remain open minded and don't buy into any particular belief system regarding what AP is.