I am the LORD your God, who brought you up out of the land of Egypt.
Open your mouth wide, and I will fill it.--Psalms 81:10 (ESV)
Why do we do devotions? Why do we read our Bibles, pray, go to church, and sometimes even fast? The Bible says that we are not saved by these duties, so what's the point of doing them?
The point is: Spiritual disciplines are "opening our mouth" in God's direction. Duties like meditating on Scripture and fasting are means which God uses to give us joy. He promises in this psalm that when we look to Him for satisfaction, He will fill our hungry souls and satisfy us with "honey from the rock" (verse 16).
The exciting promise in this verse is "Open your mouth wide, and I will fill it." No matter how wide we open your mouths, he will always more than satisfy us. No matter how much we read our Bible, there will always be more truth to ignite our hearts. No matter how much we pray, we cannot exhaust God's blessings. In fact, the greatest hindrance to our happiness and satisfaction is not our circumstances but our own laziness in spiritual disciplines.
Look at your spiritual duties not as a way to earn God's favor but as a way to open our mouths toward God for joy--He will satisfy you.