It seems to me that if your purpose in life before your deconversion was to get into Heaven, that life was truly meaningless -- as if you were devaluing your real life on Earth by setting your sights on an afterlife for which you had no real evidence.
But, if, as a Christian, you thought one of your purposes on Earth was to help people, what's preventing you from doing that as an atheist?
We all make our own purposes in life. It's nice to live your life without fear of some nasty deities messing it up. That is one reason many (maybe most) atheists who were former Christians enjoy their new life more than the previous existence of being slaves to a fiction.
But, if, as a Christian, you thought one of your purposes on Earth was to help people, what's preventing you from doing that as an atheist?
We all make our own purposes in life. It's nice to live your life without fear of some nasty deities messing it up. That is one reason many (maybe most) atheists who were former Christians enjoy their new life more than the previous existence of being slaves to a fiction.