In John 14 when Jesus was about to go to the cross he tells his disciples He will send the Holy Spirit to help them. Then he describes what the Holy Spirit does. As Christians today the Holy Spirit still helps us.
1) The Holy Spirit leads us into all truth
15 “If you love me, obey my commandments. 16 And I will ask the Father, and he will give you another Advocate, who will never leave you. 17 He is the Holy Spirit, who leads into all truth. The world cannot receive him, because it isn’t looking for him and doesn’t recognize him. But you know him, because he lives with you now and later will be in you.
2) The Holy Spirit teaches us everything and will remind us of everything Jesus tells us in the Bible
25 I am telling you these things now while I am still with you. 26 But when the Father sends the Advocate as my representative—that is, the Holy Spirit—he will teach you everything and will remind you of everything I have told you.