Knowing about someone and actually knowing them are two different things. Jesus wants us to know Him, not just know about Him. Because we are earthly, finite creatures with a less than perfect nature, knowing Jesus is a life long process, but one that has eternal rewards.
Jesus on the other hand is perfect. He knows us completely. To be truly known is to be loved and understood on the most intimate of levels; only Jesus is capable of this. St Cyril of Alexandria puts it this way: "I know mine means I will receive them and give them a permanent mystical relationship with me." St Thomas Aquinas, in the voice of Jesus, tells us why those who follow Jesus hear Him: "The very fact that they hear Me is due to the fact that I know them by an eternal election."
These two saints show us that by the beautiful and simple fact that Christ knows us, He offers us a deeply personal and intimate relationship with Him.
The last recorded words of Jesus are "Follow Me." (John 21:22) In those two powerful words, Jesus offers us an invitation. It is an invitation to that permanent mystical relationship. It is an invitation to allow Him to shepherd us, to be part of His flock. If we are open to hearing His voice, it is because He knows us. He does not call us as a general collective group, but individually, each of us by name.
As with any invitation, this one too can be either accepted or rejected. If we accept Jesus' invitation to know Him, love Him, and be known by Him, we will always hear His voice and we will follow Him. This invitation from Jesus is an open one. If we ever refuse it, we can always return to Him, asking His forgiveness, and telling Him that we now want to accept this invitation.
This path of the Good Shepherd, albeit strewn with crosses, will lead us to the Father and eternal life.