Hardening is a decision which is preceded, as with many decisions, with deliberation and the cultivation of taste. In the time period of deliberation, we hear things from other people that can affect our decision-making. These words work in us, and we amplify them within ourselves. We certainly can't be said to have decided one way or another. And yet in the moment of stress, we make some kind of decision, which perhaps was latent in us beginning at some point in the deliberation process. We had some kind of pattern of behavior worked up in ourselves when we deliberated, which can then take over us in the moment of decision. When was that decision really made? At the "moment of truth"? Or long before, when we were deliberating? So though it may seem as though we are far from positively rejecting God, we may be preparing ourselves to reject him in the future, and that preparation itself is a kind of pre-hardening, which is the decisive danger.
If you worry about your salvation and do not know that you have rejected God, you haven't, but your deliberation may still have put you in danger. There is still time to amplify the part of you who loves and trusts God fully, and desires to come into tune with his preferences fully by overcoming all of your sinful habits.