The rivers of Babylon represent the currents of confusion and sense consciousness that we cannot pull ourselves out of at times. These are the times that try us, when we get caught in this current inevitably we feel totally out of control of our lives and the events in our lives. We can understand why the psalmist wept when he remembered Zion, which is a loving, peaceful state of mind. Often when we are caught up in sense consciousness we are told by the media, our friends and our families that we should be happy about the material things we have attained. However we feel unhappy and in bondage to our house, our job or whatever may be the problem.
How can we feel happy and sing the songs of the Lord in a foreign land (when we are not at home in our comfort zone)? But this is exactly what we need to do, to refocus on the good in our lives and the good we want for our lives. If we do not set peace of mind (Jerusalem) above all else, we are ineffective (without a right hand and tongue cling to the roof of my mouth).
Remember how the carnal thoughts and tendencies (Edomites), the psalmist cried tore down my peace of mind (Jerusalem). These confused thoughts (daughters of Babylon) are very destructive. Happy are those who dash your offspring (thoughts) on the rock. In order to overcome these thoughts one must break them apart with faith in God (the rock).
And so it is! Amen!