I know what you mean about feeling like it's biologically based and sometimes irrelevent to events in your life. But lately in CBT I've been making some breakthroughs that've made me understand my anxiety alot better (and the fact that not being able to cope with my anxiety leads to depression). It's still really painful to go, and everytime I cry.

And talking about it just makes me feel worse for the rest of the day... which in itself implies that I may be blocking out/denying some of my disfunctional feelings and thoughts EVEN though I feel completely carefree and happy before therapy sessions.

I think that there's always some kind of dysfunctional belief that underlies your depressed/anxious feelings, and causes your neurotransmitters to behave as they do -- although at times it's one that's buried so deep that we can't begin to recognize it.