Self assurance, is not found in humility. To be self confident in your state of being, is not in the nature of a "True Christian". Did not Jesus Christ say, "If any man will come after me, let him deny himself, and take up his cross and follow me." Matthew 16:24 Self denial does not allow self assurance, self confidence, or self determination. Jesus Christ requires total submission and trust in God.
"And he said unto his disciples, Therefore I say unto you, Take no thought for your life, what ye shall eat; neither for the body, what ye shall put on. The life is more than meat, and the body is more than raiment. Consider the ravens: for they neither sow nor reap; which neither have storehouse nor barn; and God feedeth them: how much more are ye better than the fowls?
"And which of you with taking thought can add to his stature one cubit? If ye then be not able to do that thing which is least, why take ye thought for the rest?
"Consider the lilies how they grow: they toil not, they spin not; and yet I say unto you, that Solomon in all his glory was not arrayed like one of these. If then God so clothe the grass, which is to day in the field, and to morrow is cast into the oven; how much more will he clothe you, O ye of little faith?
"And seek not ye what ye shall eat, or what ye shall drink, neither be ye of doubtful mind. For all these things do the nations of the world seek after: and your Father knoweth that ye have need of these things. But rather seek ye the kingdom of God; and all these things shall be added unto you.
"Fear not, little flock; for it is your Father's good pleasure to give you the kingdom." Luke 12:22-32
David's heart was perfect with the LORD, "Because David was right in the eyes of the LORD, and turned not aside from anything that he commanded him all the days of his life, save only in the matter of Uriah the Hittite." I Kings 15:5
Although David's only sin, all the days of his life was, the sin he committed against Uriah and Bathsheba, he never ceased to ask God to forgive him for his many sins including those he was not aware that he committed. That is the nature of a "True Christian!"
Apostle Paul warned against self assurance and self confidence when he said, "Wherefore let him that thinketh he standeth take heed lest he fall." I Corinthians 10:12
He followed his own admonition when he said, "Be ye followers of me , even as I also am of Christ." I Corinthians 11:1 He also said, "Know ye not that they which run in a race run all, but one receiveth the prize? So run, that ye may obtain. And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible.
"I therefore so run, not as uncertainly; so fight I, not as one that beateth the air: But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway." I Corinthians 9:24-27
Apostle Paul knew that even though he was called and ordained by Jesus Christ himself, that if he were not diligent and careful, he could lose out, and become a castaway if he failed to follow Christ selflessly.
Even Job knew, though God himself, vouched for his perfection, he could not justify his own state of being. He said, "If I justify myself, mine own mouth shall condemn me: if I say, I am perfect, it shall also prove me perverse." Job 9:20
A "True Christian" is too humble to declare his state of perfectness by saying, "I am a Christian". The statement itself, according to Job, proves the speaker perverse. To say, "I am a Christian", is by definition of the words, to say, "I have reached the perfection of Jesus Christ himself". That is too audacious, self confident, and self assured, to be the words of a "True follower of Jesus Christ". It is not humility.
Did not Jesus Christ himself say, "If I bear witness of myself, my witness is not true." John 5:31