God's word is active, alive, penetrating, exposing everything

Hebrew 4:12-17
The word of God is alive and active.it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart. 
Since we have a great high priest who has ascended into heaven, Jesus the Son of God, let us hold firmly to the faith we profess.
Let us then approach God’s throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need.
The writer has being arguing from God's word: now he steps back to consider it.  alive, active, penetrating, exposing everything to the One to whom all must be account.
The write moves on from Jesus ,as the Son of God, to Jesus, our greatest high priest. A title given him nowhere else in the New Testament.
Why?
God knows us everything, nothing can be hidden from Him, thank Jesus who knows our weakness and would not emphasizing it, so let us hold firmly to the faith.
God's word can penetrate our heart and gives us clear mind to make right decision.
How?
Confidence to what we believed and carefully listen his words.