I wanted to conclude the Shvuos mayseh with Reb Aharon by saying that at that point Reb Aharon kissed Shlomo and said he was destined for greatness.
As far as depression goes, I doubt Reb Shlomo was depressed all the time, but the Holocaust weighed on him heavily, as did any tzara experienced by any Jew, anywhere. He literally died of a broken heart, as was said at his levaya. (I think six Israeli soldiers died that week.)
When it came time to prepare for kvura, the family had to take up a collection to pay for the levaya. The richest and most successful Jewish singer of all time died completely broke. He had given every last penny he had to the less fortunate, as he did his entire life. According to Rabbi Abraham Twerski, that was the biggest shevach of all, and summed up his whole life.