That doesn't mean that we don't have a part to play in discovering truth. In John 8:31-32 we read about Jesus teaching a crowd. Butler in his commentary describes the crowd as:
a group of the Jews here at the Feast of Tabernacles who had, in some way, manifested a superficial belief in Him. They wanted to believe in a Messiah, but not the Messiah. They were willing to follow, fight or die for a temporal King, but they would have none of a spiritual King who demanded sovereignty over their motives and deeds. They would gladly serve Him with their lips, but not their hearts. (p. 54)
This was not the most sympathetic of crowds. They were willing to listen as long as Jesus told them what they wanted to hear. So we see this crowd turn from belief to one with murderous intentions (see John 8:59). It is in this context that Jesus makes this statement; "You are truly my disciples if you keep obeying my teachings. And you will know the truth, and the truth will set you free" (John 8:31-32; NLT).
First I need to point out that a disciple of Jesus is first and foremost one who obeys His teachings. This is why in the teaching of the Final Judgment (Matthew 25) God separates the redeemed from the unredeemed based on their actions. A true disciple of Jesus will live out the teachings of Jesus.
This ponder was motivated by the simple word "and". It seems here that Jesus is saying that through our obedience we gain a greater understanding of truth. Without obedience we cannot hope to know truth. Obey Jesus and know truth.
Aside from intentional time of reading and studying Scripture, our part of knowing truth is found in obedience. Only through obedience do we experience God's truth as a reality in life. If we want to know truth then we have to actively obey Jesus.
Why would this be the case? I would imagine it has something to do with throwing pearls before hogs (Matthew 7:6). If we are not going to obey the teachings of Jesus that we already know then we are not going to obey a new teaching or truth that the Holy Spirit desires to reveal to us. Such a teaching would be a waste on us.
So the question we need to consider is: Am I doing my part to know truth? If we are struggling to hear from God it maybe because we are unwilling to to do what He has already told us to do. Obey and allow truth to move from your mind to your heart.