I wouldn't go so far as to suggest that not having collaborators is the death of the muse, at least for myself! For me it's more important to live life fully, experiencing plenty of new things to inform my craft; and have plenty of people around me to observe and occasionally parody as characters. But I do agree: writing is the breath of life. I put everything that happens to me into my stories. They've become sort of shock-absorbers for any personal drama in my life.