No need for a therapist, no need to act out in potentially destructive ways, not when you can empty yourself of everything difficult through your fingertips.
Some composers are better than others for that. Chopin, Schubert, and some Beethoven, are marvelous for their cathartic effect - you can overplay them when alone, without fear of criticism from one's piano teacher, and be self indulgently self-pitying or angry, playing yourself into every note, and feel better afterwards.
But Bach is what I played when things seemed so bad that the thought of catharsis was dreadful and unbearably naked, when the last thing I wanted to do was play myself into the music. Because Bach was always... wholly Bach.
I placed an Amazon.com order last Friday and received it today. I am on page 67 of my newly acquired copy of Madeleine L'Engle's The Small Rain and just read this:
Katherine looked down at the keyboard. "Mother said when you were unhappy or confused, Bach was the person to play. With almost everybody else you can think, but with Bach there's nothing but the music. It's true, you know."
"Yes, I know," Tom said. He stood leaning on the piano. Twice he seemed about to speak; then he waved his arms a little, helplessly, and wandered out.
The best writers can do that - magically pull out something important, and mostly forgotten, from your own experience, phrase it far better than you could have possibly done so yourself, and remind you of it.