The "Trisagion" or "Thrice Holy" by itself is a simple vocal prayer addressed to God, describing three qualities of His being that are repeated three times. Notice how this prayer names God divine, strong, and ever-lasting. While these are complex theological propositions in and of themselves, the pure simplicity of the expression aids you in approaching God with a sense of awesome wonder, while then finishing with a heartfelt plea for His love and mercy.
Pray this unceasingly! Then, stop using the words. This will launch you into a silent and still meditation where the Energies of God will reach down from Heaven to show you who you were before creation and lead you to where He wants you to reside with Him for all eternity!
"Holy God, Holy Mighty, Holy Immortal: have mercy on us" (repeat 3x).