I firmly believe Jesus knows us ...it would seem that He is saying we never really knew Him.   It's the relationship that we develop.   If we don't follow what He says, don't even attempt to do what He desires, and our behavior is contrary to what He inspired the apostles to be ...then where is the relationship.   We do not have to be persecuted like His apostles were to have "relationship" ...it's in relation to what He said.   I didn't always follow after my earthly father ...and my dad would say I love him, and I'm understanding more and more how he loves me, and has loved me ...and mom too.   Many sinners (we are all sinners) would say they love Jesus, and Jesus obviously knows us.  We have confessed some things ...and on occasion repented, some of us with tears.   That's all good, but that in itself does not account for what is really important ...that we acknowledge Him for who He is, and accept His life into ours.