I have often tried to figure it out... or rather the reasons for these fears - and the explanations range from psycho-emotional exhaustion due to intensity with which she lived, to the fact that she was a premature child, whose body oozed blood when she was born (thus the permeability of ego-boundaries, etc., etc.)... Some time I also tend to believe that these fears were the encounters with the alien in her, which was so manifest in her poems like the "Private Demons"...perhaps ultimately it was these which won the psychophysical battle of her life...
But this "figuring out" remains, but the useless attempts of the rational mind. The experience for her, was something far more deeper and encompassing....
...I’d said earlier that I didn’t want to go, I had to go - that’s it - it is a sense of urgency in me to go, just get out, and don’t care about where you go - I am afraid, afraid not only of the closed rooms and people in it - but also of this horrible sense of urgency in me - I am afraid of doing something drastic, but I am helpless in the hands of some unknown power as well as myself. I begin to hate myself and I could gladly kill myself - but it is the least I can do to go away and be away from all persons for some time -... it is too big - it is an overall phenomenon, not a simply unpleasant sensation or feeling.
Oh, fears you can classify into various types - fear of sex, of violence, of darkness, of lonliness, of closed rooms, of faces, of yourself, of the unknown - but it has a specific cause behind it - this is different - it is an overall fear - not fear, something inexplicable and absolutely wild...