Note 41 at Jn. 14:28: Jesus is saying that if the disciples were thinking of Jesus more than they were thinking of themselves, they would be happy that Jesus was returning to the Father. This is always the case when a believer is taken from us in death. There is no reason to sorrow for the one who is gone; he is blessed beyond measure. Our sorrow is really for ourselves.

Even from a selfish standpoint, the disciples had no reason to grieve because Jesus would return to them through the indwelling of the Holy Spirit. As He explained in the next few minutes, it was actually more advantageous to the disciples for Jesus to leave and send back the Holy Spirit (see note 75 at Jn. 16:7, p. 440).

Note 42 at Jn. 14:28: Jesus had already stated His union with the Father so clearly that He had been accused of blasphemy more than once (see note 3 at Jn. 10:30, p. 280). This statement about the Father being greater than Jesus must harmonize, not contradict these other claims.

A key to understanding this is given in Philippians 2:6-8 where Paul states that Jesus didn't think it robbery to be equal with God but humbled Himself, taking on the form of a servant (speaking of His humanity). Jesus was equal to God in His divine nature but He made Himself inferior to the Father in regards to His humanity. Jesus didn't lose any of His deity when He became a man, but He did clothe it in flesh and submitted to the consequent limitations. In this sense, the Father was greater than Jesus.