"But the Counselor, 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" (John 14:26 RSV).
This verse is from Jesus' final discourse to his disciples on the occasion of the Last Supper, as his mortal ministry was drawing to a close. He is reassuring his disciples that, even though he will no longer be with them in physical form, he is not abandoning them. ("I will not leave you desolate," v.18.) They won't need to rely on their memory or understanding of his teachings; "the Holy Spirit" will be with them. This Holy Spirit is depicted in Acts 2 as tongues of fire. The important point, I think, is that this spiritual guidance is not external but internal. They no longer need an outside person or source to provide the understanding that will allow them to continue on their own paths. That guidance, that spiritual power, is now within them. (It's always been there, of course, but their focus on Jesus as the source of guidance has prepared them to recognize it.)
It is so for us, as well. For much of our personal path, we will need the guidance and support of spiritual teachers and religious structures. And when we're centered and ready, we will learn to find that guidance within, in the indwelling Presence that is our true identity.