I have read some of your posts and you have written many good things. More than once in my life, I have gotten really depressed. I have always been able to bounce back (though the last time I was depressed it lasted for years; it was very extreme).
Venting some of my feelings on here, really helped me with some of my depression. There are also some very kind people on this forum who sometimes simply send "how are you doing?" types of private messages so for me, it was beneficial to expose myself. As far as feeling like you are losing "value" because you have shared something about yourself, could this be a bit of paranoid thinking? One of the things that made my depression so deep was that while I am not at all psychotic, I did make assumptions about people being "out to get me." The only way I was able to get a handle on some of it was by working with my therapist.
I am sorry you feel so isolated. Yes, I think depression usually gets started (and is harder to overcome) because of isolation and/or other stresses we face that overwhelm us. At least you are not alone in the sense that many others at this forum are depressed, in part, due to isolation.
Do you work? Exercise? Go to therapy. I find that activities are helpful. I hope that something in this post might be encouraging to you.
PS I think that Rose76 is right. And I think I have seen a study or two (there was at least one I read about a year ago) showing that intelligent people experience more mental health issues than those of us who are just average. This makes sense to me.