John Calvin, commenting on Nicodemus’ question to Jesus in John 3:9 (“How can these things be?”) says:
There is no worse obstacle to us than our own pride; for we always want to be wiser than is proper, and therefore we reject with devilish pride everything that is not explained to our reason, as if it were fair to limit God’s infinite power to our poor capacity. We may indeed inquire into the manner and reason of God’s works to a certain extent, with sobriety and reverence. But Nicodemus rejects it as a fable with the objection that he does not think it possible.
Indeed. How often we get frustrated, angry, or just plain ambivalent towards God because we do not understand His ways. It is as if we want to be able to trust in God without faith getting in the way. Faith is that which keeps us trusting even when we do not fully understand or see. Faith is what sustains us in this time between the times, living as we are between the ascension of Christ and his parousia (return).