Although Jesus would leave His disciples when He was crucified, and leave them again when He went back to heaven, He assured them that He would see them again (John 14:18).  He wanted them to anticipate that the relationship they had enjoyed together would continue, and even more closely than before.  After His death, Jesus would be raised to life and the disciples would see Him (1 Corinthians 15:3-7).  His resurrection would also confirm His promise that all those who believed in Him would also be raised to new life on the Last Day (John 6:40).
 
But until then, their lives would be different.  After Pentecost, when they would be filled with the Holy Spirit, they would understand the reality of being in close fellowship with the Father and Son; even though they would not see them.  Then there would be ongoing fellowship with God, as the disciples obeyed what Jesus taught them.  The bonds of love would strengthen the more they obeyed; and they would experience God the Father, God the Son and God the Holy Spirit making their home inside the heart of every believer (John 14:23).

The concept of Jesus being ‘in the Father’ is a way of saying that Jesus shares the same nature and character as Father God.  Jesus’ life on earth was so bound into the loving plan of the Father that He never spoke or acted independently from Him.  That was the way He wanted the trainee apostles to relate to Him – only speaking and acting in His Name.  And Jesus wanted to make clear that He would live in them too, to guide and empower.  Jesus later prayed that these special relationships might also be for us who have believed the Apostles’ message (John 17:20-23).  
 
Although many people today may claim to know and love God, the test is always seen in obedience.  Those who obey Jesus are the ones who love Him.  And those who love like that will also be loved by all of the Godhead.  So, although it is easy in some places to sing worship songs, and even tell people that you are following Jesus, obedience is the test.  And when we fail to obey, repentance is further evidence that we know what is right and that we want to turn back from our bad ways to do whatever will please Jesus.  Such people have the privilege of an ongoing relationship with God that is transparently life changing.  Is your life like that?  If not, where are you being disobedient?