Although the Almighty is beyond the power of human understanding to grasp, Christians believe that knowing God's Will is possible because Jesus, in his humanity offered for our sakes, has given us real access to God.
The kind of knowledge the Risen Lord gives us is different than the merely factual kind of knowing. Such factual knowledge is all about simply knowing what to do - how to make or fix something. There is nothing to be gained in approaching the Mystery of the Living God like a service manual.
Knowing God and his Holy Will is, instead, deeply personal. In this loving knowledge, St. John of the Cross explains, love (not naked reasoning) leads us forward into the Divine Mystery. What the intellect understands follows behind our love for the One who discloses Himself. The loving will knows the Loving Will of God and a union of wills, each given to the other, becomes possible. This love is a friendship love - it sees the goodness and beauty of God because it has loved Him and been loved by Him first. St. Paul calls this the Wisdom of God (see 1 Cor. 6-13). Some theologians call this experimental or experiential knowledge of God. There really is not words to describe this kind of knowledge - yet those who know the Lord in this way really have something to say, something the world needs to hear, something we need in our lives.
With this kind of loving knowledge, a joy, peace and a dynamic self-possession grows in the heart. Every time someone acts in accord with this loving knowledge of God, these fruits increase -sometimes exponentially. This fruit, which St. Paul enumerates in his letter to the Galatians, is produced by the Holy Spirit (Gal. 5:22). When we choose to act in accord with the loving knowledge the Lord shares with us, it frees the Holy Spirit to be fruitful in our hearts.
It is possible to act against this knowledge, to act as if we were ignorant of God. St. Paul warns against living with our minds conformed to this age or like those whose minds are darkened (Rom 12:2, Eph. 4:18). It is possible for those who believe in Christ to choose to live in the flesh - to allow the unconscious hidden drives of our nature to make our decisions for us, not only in big things, but especially in the little things we think no one knows and no one will be hurt by. This living in intentional ignorance is what keeps us immature spiritually - acting against what we know in our hearts.
There is no reason for discouragement if we suddenly realize that most of our lives we have chosen to live in ignorance. Teresa of Avila lived like this until she was almost forty years old. The Lord however would not let her continue - and when she was off her guard, He pierced her to the heart with His Love. Just as He touched her to the core, He can touch any one of us - it is something worth asking for, something worth enduring every kind of trial to obtain.
So the spiritual life really begins when we take up the struggle to make room in our lives for the loving knowledge of God that only Jesus gives. This is why Christians must make silent prayer a priority in their lives. It is a knowledge that comes from the Cross and doing all we can to gain this knowledge is worth it.