We frequently see in the Gospel the friendship the Apostles had with our Lord: they spend time chatting with him, asking him about things they don’t understand. The Gospel mentions one of those incidents: it’s a topic which must have come up often, especially towards the end of our Lord’s life.
Our Lord said to them: He who has my commandments and keeps them, he it is who loves me; and he who loves me will be loved by my Father, and I will love him and manifest myself to him.  In Jesus’ day it was commonly held among the Jews that when the Messiah arrived he would reveal himself to everybody as King and Saviour. The Apostles thought that our Lord’s words referred to them, to those who were close to him, those who loved him. Judas Thaddaeus understood what our Lord was saying, and he asked Lord, how is it that you will manifest yourself to us, and not to the world?
In the Old Testament, God revealed himself on different occasions and in different ways, and he promised that he would dwell in the midst of his people. But now our Lord is referring to a very different kind of presence: his presence in the people who love him, in each person who is in a state of grace. If a man loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him.  This is the presence of the Blessed Trinity in the soul which has been reborn through grace. This is a fundamental teaching of the Christian life frequently repeated by St Paul: For we are the temple of the living God,  he says to the first Christians of Corinth.
Quoting this passage, St John of the Cross comments: What more desirest thou, O soul, and what more seekest thou without thyself, since within thyself thou hast thy riches, thy delights, thy satisfaction ... thy Beloved, Whom thy soul desires and seeks? Rejoice thou and be glad in thy inward recollection with Him, since thou hast Him so near. 
We should learn to become better and better friends of God who is dwelling within us. Through this divine presence, our soul becomes a miniature heaven. Reflection on that thought can help us enormously. At Baptism the three Persons of the most Blessed Trinity came into our soul: they want to be closer to us throughout our lives than the closest of friends. This presence – which is quite unique – is lost only through mortal sin. But we Christians should not be content with simply not losing God’s presence within us: we should recall his presence within us in the midst of our daily activity, when we’re going from place to place, to thank him, to ask him for help, to atone for the sins we commit against him each day.
At times we think that God is far away, whereas in fact he is very close to us. He is more interested in what we’re doing than the best of friends. Reflecting on this ineffable closeness of God, St Augustine exclaimed: Late have I loved you, O Beauty so ancient and so new, late have I loved you. For behold you were within me, and I outside; and I sought you outside ... You were with me, but I was not with you. I was kept from you by those things, yet had they not been in you, they would not have been at all. You called and cried to me and broke open my deafness. You sent forth your beams and shone, and chased away my blindness. 
But to talk to God, really present in our soul in grace, we need to control our senses, as they tend to scatter and become attached to all sorts of things. We need to be aware that we are temples of God and to behave accordingly. We need to surround with love, with resounding silence, that intimate presence of the Blessed Trinity in our soul.