You've finally circumvented the Yetzer (evil inclination), and now you're all set for a beautiful hour of Hisbodedus (personal prayer - speaking to Hashem in your own words - alone - with no one else around). You take a walk in the park, out in the field, or down by the river, you open your mouth - wanting to pour your heart out to Hashem - and nothing comes out! How frustrating! What a letdown.
Don't fret; here's what to do when the words don't come - sing a niggun! A niggun (melody) uplifts the soul, puts wings on your heart, and breaks the grip of the vise that the Yetzer has clamped on your mouth (the last thing he wants you to do is to talk to Hashem!). After singing a niggun for a few warm-up minutes, the words of personal prayer and love for Hashem will flow forth like a fountain.
When I have this problem, I take a flute and start playing whatever comes to me wherever I am in our beautiful homeland. Then, the right words flow forth. That's how Calming Waters, Judean Dream and Whispering Soul came into being. King David used to do the same thing. Have a wonderful day, and may you always have a song of the Land of Israel on your heart!