...Ben, I don't know of anyone who is 'free' of all insecurity. I have insecurities. I know other Christians who have expressed insecurities of various kinds. These feelings of inadequacy and uncertainty aren't something that will just go away for us if we enact some specially prescribed thought or action.
So, in essence, knowledge for me isn't the holding of some inviolable truth that can't fail, but rather having a generic sense of assurance that I'm heading in the right direction. Each of us is a work in progress in all modes of our common humanity as we stand before God. So, I don't think it should be our primary goal or expectation to think we can find a perfect formula by which to arrive at some definable point of certainty in life. Even the apostle Paul, who was big on accentuating the importance of biblically contextualized notions of Wisdom, Knowledge and Understanding, said that:
Philippians 3:12-16 New International Version (NIV)
12 Not that I have already obtained all this, or have already arrived at my goal, but I press on to take hold of that for which Christ Jesus took hold of me. 13 Brothers and sisters, I do not consider myself yet to have taken hold of it. But one thing I do: Forgetting what is behind and straining toward what is ahead, 14 I press on toward the goal to win the prize for which God has called me heavenward in Christ Jesus.
15 All of us, then, who are mature should take such a view of things. And if on some point you think differently, that too God will make clear to you. 16 Only let us live up to what we have already attained.