I have yet many things to say unto you, but ye cannot bear them now.
Note 80 at Joh 16:12: The Lord doesn't reveal to us things that we cannot receive. This is why we sometimes fail to get a response from God when we are petitioning Him for answers. It's not that God is unwilling to respond; it's that we are unable to receive. The way to overcome this hardness of heart (see note 3 at Mr 8:17) is to yield to the ministry of the Holy Spirit that Jesus began to describe in Joh 16:13.