I've seen this suggestion before for "curing" atheism:
Truly try to believe in Christianity for a month. Just 30 days. Give it a shot, because it can't hurt anything.
I don't know that I've ever met anyone for whom atheism was a choice, who just decided one day that the whole belief thing is a drag, so fuck it, I don't believe anymore. Most atheists I know were believers at one point, including myself. I was horrified when I realized I didn't believe anymore. I panicked, in fact, desperately trying to believe in something, anything. I felt lost and abandoned and betrayed. For the very first time, I felt my mortality, a real heaven-free mortality, and I did not like it.
I tried so hard to believe. I just couldn't.
It doesn't work. If you don't believe me, try believing, sincerely, for a mere 30 days, in invisible pink unicorns. You can't, no matter how hard you try. You know damn well invisible pink unicorns do not exist, and once you know that, there's no going back. Not for 30 days, not for ever.
Trust me, I tried.