No one is half-regenerate or semi-regenerate; you are either born of the Spirit of God or you are not. Regeneration, which is that work of God by which we are transferred from the kingdom of darkness into the kingdom of light, is a real work of conversion, and it happens instantly by the work of the Holy Spirit, so that a person is either in that state or not. There is no process of regeneration; it is instantaneous.
But if that’s the case, doesn’t that raise suspicions about people who cannot state the day and the hour of their conversion? No. We need to distinguish between a conversion and a conversion experience. Furthermore, we need to recognize that not everyone is instantly aware of the moment when the Spirit of God does His supernatural work within his or her soul. That’s why it’s very dangerous to create categories by which we evaluate people whose experiences do not match our own.
God the Holy Spirit may regenerate a person a week, a month, or even five years before he experiences the reality of what has already happened internally. So even my confidence with regard to a particular date and time of conversion applies only to my experience of conversion, not to the fact of it, because we can fool ourselves in terms of our experience.
Actually, one of the most dangerous things we can do as Christians is to determine our theology by our experience, because no one’s experience is normative for the Christian life. We have to determine our theology from the Word of God, not from what we feel. Not only that, we are open to misunderstanding and misinterpreting the meaning and significance of the experiences we go through. That’s why we are called to check our experiences against Scripture, so that we define our faith by what Scripture says, not by what we feel or what we experience. If we rest our assurance on an experience and not on the Word of God, we’re inviting all kinds of doubts to assail us in our pilgrimages. We need to seek authentic knowledge of our salvation, not just some warm and fuzzy experience. — from “Can I Be Sure I’m Saved?”