Why be open to the Holy Spirit? This question is important because the only link between us and the Throne of Grace is the Holy Spirit.
If he is quenched (1 Thessalonians 5.19) or grieved (Ephesians 4.30) we have almost certainly cut off the only link that will let us know how God is moving today, not to mention forfeiting any real intimacy with God (1 John 1.3). We must, therefore, maintain the best possible relationship with the Spirit.
Although God is the same yesterday. today and for ever, and therefore unchanging in his nature, he is not unchanging in the way he reveals himself, and does not always reveal himself in one generation as he did in another. We must therefore be open to the Spirit less we miss the way in which this God sovereignly chooses to manifest his glory.