I prefer... its not what you believe you are, that makes you a christian, its you really are.. i.e. "You MUST be born again"- Jesus.. Its whom you are not whom you think you are..
Humans are given to 2nd realitys.. As many Jews worked against God's plan in the old testament (thats why God whistled for Babylonian and Assyrian rulers to take them captive) and (some did learn from that experience) each time.. Same with being a christian..
Some approach spirituality as a club and as a club member with fund raisers, titles and all that.. others as a family with family duties around "the House".. It might be impossible to be born again and not know it.. Some christians are simply not christians(family) its not a matter of sanctification.. Expecting a club member to be a family member is a serious mistake.. expecting the club member to perform duties not possible.. or faked.. you know, mimicked..
Bornagainology is not very scientific, thank God..
Any formulae are laced with too much infinity to be practical..