In these few simple words, the verse emphasizes the wonderful attributes of our heavenly Father, His unsearchable greatness, His glorious majesty, and His mighty power, as well as the splendor of His kingdom.
David came to understand that the only way to live a successful and victorious life is always to remind ourselves of the unsearchable greatness of our praise-worthy God forever. The words of this Psalm are a constant reminder that no matter what injustices we face in this fallen, sinful world, there is a God Who deserves to be praised for all that He has done for us - both now and throughout eternity.
As we wake up in the morning and sing our song at night, may our thoughts and songs of praise to our heavenly Father fill us with His glory. As we contemplate His never-failing love and everlasting kindness, may we be filled with joy as one to sound the trumpet of praise in unison? “Great is the LORD, and greatly to be praised, and his greatness is unsearchable.”

Dear Heavenly Father, thank You for being our God, and I praise and thank You for being worthy of our continuous praise and worship. Each day may I fill my heart with songs of thanksgiving and praise for who You are and what You have done for us. Great LORD, we have trusted in You for salvation. Please do not let us forget Your unsearchable goodness and grace to all of Your children. 
In Jesus's name I pray. Amen.