Spiritually maturity is the ability to live with a sense of "reasonable" assurance. This is what we generally do. Absolute assurance does not exist. Somewhere deep within our souls this truth nags at us (as it is the "still, small voice of God") even where dogmatic formulas are fabricated to deny this truth. God Loves us, and therefore does not want us to fall victim to "presumptuous sins" which will rob us of Eternal Life. Thus he knocks at the door of our hearts, not wanting us to become deceived into thinking that all is well with our souls in spite of our continuance in the death of sin. There will be many, our Lord tells us, who presumed themselves to be His servants, thinking that they believed in Him, but who did not do the will of God, but rather, continuing to sin did not ever really come to the knowledge of God. To these He will say "depart from me... I do not know you".
Because He is Love, God created us free to choose between Love and sin. We'll all be answering to Christ for our own choices. Thus, I said, in concert with Holy Scripture, that we must persevere in the faith, continuing to abide in the vine which is Christ, for our adversary, the devil, continuously roams about as a ravenous lion looking to devour souls by temptation and deception.