Who's in control?!

I've just been prescribed citalopram for panic attacks and depression. I can't seem to shake the idea that depression is a perceived lack of control. For instance.... I do not want to die. I would not willingly commit suicide... I see it as both illogical and as being against my plans for life. So, if I am in control of my will... then how would/could any mood drive me to do something I don't want to do? I am scared, because depression is always portrayed as going hand in hand with suicide. I have to answer questionares about how often I think about suicide. This, to me, implies that a time may come when I'm suddenly overcome with some strange suicidal force. Is this true? Could I be driven to such a thing given the right brain state? Basically, I'm either in control or i'm not in control... so if depression got so bad that I was driven to suicidal atempts... then surely I'd lack the will to snap out of it? i.e. once you're in that place you're not getting out.

or maybe those thoughts are symptomatic of the so called "black and white" depressive thinking.

you see... depression can be analysed... I have depression and I like to be introspective.... but this is just a mind ###$. I feel $#%^... true... and I find it hard to do anything... true... but is this due to depression or is it due to me thinking I lack control?