Kyle Gann has been hosting an interesting discussion about what composers talk about (and think about) over at Postclassic, and I feel the need to add a cent or two--or perhaps a sentence or two in response.
The idea, of course, that I can get into someone else's head, especially the head of someone who is no longer alive, is absurd, so I can only speak for myself.
Music, being made mostly of feelings (though it can and should be organized in some way with the mind in order for those feelings to be transmitted either by a composer to the person or people playing the music, or by a performing musician to an audience), can be understood in relation to any number of different emotional situations by any number of different listeners. It is not my business as a composer to write a narrative, but I suppose it is my business as a composer to make an abstract narrative possible for both players and listeners. I also don't think that it is a future audience's business to know what my particular personal problems were when I was working on a piece of emotionally-charged music. Actually, I would prefer it if they didn't know.
Feelings are complicated. I imagine that I'm not alone when I say that I have used writing music as a ladder of escape out of a difficult emotional state. Sometimes just doing the work itself tends to help. Having a "place" to wallow and scream over and over again is a luxury, and it is great when it can have creative spoils. Perhaps hearing the piece after a period of months or years brings back the memory of having had difficulties, but once the details have been blurred by the kindness of time, the music takes on the emotional life of the moment and the emotional life of the performing musicians.
I wrote a piece for a friend while I was going through a difficult time. She asked me, in search for a way to interpret the piece, what it was about her that caused me to write the piece. The real answer is that I loved the way she played and was interested to hear what she would do with the piece, but she was far too modest to accept that as a reason. I told her that she and I were both going through some difficult personal struggles (each of us had our own life-circumstance-based struggle) during the time I was writing the piece, and the piece could be interpreted as being "about" those struggles. Her performance of the piece was very different from (and so much better than) the way I imagined the piece could be played. When she sends me her recording, I'll put a link to it here.
You don't need to know what my struggles were at the time to appreciate the music, and you don't need to know the struggles that my friend was having either. Actually, you will never know, because I will never tell.