You are looking at outward appearances. If anyone is confident that he belongs to Christ, he should remind himself that we belong to Christ just as much as he does.
KJV
Do ye look on things after the outward appearance? If any man trust to himself that he is Christ’s, let him of himself think this again, that, as he [is] Christ’s, even so [are] we Christ’s.
ASV
Ye look at the things that are before your face. If any man trusteth in himself that he is Christ’s, let him consider this again with himself, that, even as he is Christ’s, so also are we.