John 14:26 (ESV) … “But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.”
One of the most encouraging facts of Christianity is that the Comforter not only comes alongside but comes inside of us. One of the most devastating thoughts anyone can entertain when he is going through trouble is, “I am alone.” After that comes self-pity, and then the thought that “no one cares.” These are common feelings but unnecessary for the believer.
When caring for a sick child the believing parent is never alone. He is not alone in the hospital facing death, or standing over a fresh grave, or at work, or on a missionary compound. Even when we do not feel Christ’s presence, he is within us.
Much of the indwelling comfort comes by virtue of the fact that the Holy Spirit in us is, as verse 17 says, “the Spirit of truth.” The Spirit of truth indwelling us allows us to begin to understand our inner self and to see and understand something about the course of the world about us. Because of that, we are comforted. He also brings comfort to troubled hearts by reminding us of the Word of God.[1]
[1] Hughes, R. K. (1999). John: that you may believe (pp. 345–346). Wheaton, IL: Crossway Books.