i would be upset too because there doesn't sound as if there was any warmth in the correspondence. maybe your friend has gone through changes. i wouldn't expose myself because it doesn't sound as if your friend doesn't have anything to give on the emotional front. it sounds as if you were looking for an emotional connection. maybe if you wrote them and asked what was going on with their life and say you missed corresponding with them or something like that and didn't reveal what was happening in your life.
maybe they would open up and there would be an emotional connection.
it isn't fun being bipolar and so much of the time it is quite painful. i know i disconnect because i don't have anything positive to say at the moment.
love
bobby