"[I]n Scripture, God Himself is said to be angry without implying the least movement of passion. The word 'anger' is used because God's vengeance is effective, not because His nature is affective." -- Augustine, City of God, Book IX, Chapter 5
There has been some concern over whether God is affected by things outside Himself. If God's "emotions" are exactly like our emotions (the passions), then God changes and lacks sovereignty over all things. Our emotions toss us to and fro and affect our mental state. We can learn to control them with reason, but doing so is a struggle of the will. Considering God's eternal and infinite nature, it seems contradictory to say that God struggles to keep His passions under control, because this would imply that God is limited in His reason and His sovereignty by His passions. It would be saying that God is eternally conflicted.
Augustine points out a fundamental difference between God's "emotions" and our emotions. God's "emotions" are proactive, not reactive. God acts by reason in accordance with His own nature. So when we read that the Holy Spirit can be grieved over our sin (Isaiah 63:10; Ephesians 4:30), we must keep in mind that God is holy and always hates sin, as sin is opposed to His nature. God is being (eternally) consistent.