Which direction are you talking about? :o)
I swam away because of theological reasons but many Catholics have asserted (here, especially) that that isn't possible and the only reasons could have been for moral ones (i.e., disagreement over divorce, sex outside of marriage, contraception, etc.). Yet, when I left it was because I recognized that the gospel of Catholicism was NOT the gospel of Christ.
But yes, in either direction. Such a choice shouldn't be made on a whim or a "what the heck?" it seems to me.
And of what does that assurance consist, becoming a saint or just feeling justified, or something else?
If you are exposed to Jesus Christ and you willingly turn away from him, reserve your place in hell.
Catholic 101.