To say you are a Christian is one thing. For your eternal Judge to say you are is quite another. On the last Day the truth will be revealed and your opinion of yourself will NOT matter. BEWARE OF PRESUMPTION lest your assurance be deception and the shame thereof render you speechless before the King of kings as you appear before Him naked! Lest you imagine yourself to be the light of the world when according to Him you are fit for the outer darkness!
"And when the king came in to see the guests, he saw there a man which had not on a wedding garment: And he saith unto him, Friend, how camest thou in hither not having a wedding garment? And he was speechless. Then said the king to the servants, Bind him hand and foot, and take him away, and cast him into outer darkness, there shall be weeping and gnashing of teeth" (Matthew 22:11-12).
Put away therefore all boasting, arrogance, pride, highmindedness, vain confidence, etc. and humble yourself before the Lord and know your own faults, frailty, weaknesses, stumblings and entreat the Lord for mercy. It is far better for you if you fail at times to call yourself a sinner and let the Judge tell you differently on the last Day.