When I was starting to become observant, at the end of shacharis one day, someone asked me "are you finished with tehillim?". I told them I don't know what that is. They told me "if we knew what was happening in heaven while we are saying tehillim, we would be saying them all day non stop".
So, a few years later, I still would like to know what the power of tehillim is. What corrective action are we taking by saying them?