Anxiety vs. Depression

Oh, it's like the dumb old sit com premise where one person is trying to be two people.  Someone says "Where is So-and-So?"  The person who is not in So-and-So costume has to make up an excuse to leave the room and then come back as So-and-So.  In other words, they are related and connected but they don't exist together.  Below is an article that briefly introduces this partnership.
http://www.webmd.com/depression/recognizing-depression-symptoms/anxiety-symptoms

What happens is something like this:

1. I get "the trigger" as I described in previous post.
2. I just sort of flip out from the difficulty in digesting this event/realization/confrontation--whatever it is.
3. Then the flip out recedes into a state of anxiety or depression. 
4. If it's depression, the reality of this event/realization/confrontation sets in and I am helpless.  I feel invisible bonds pulling me downward, downward.   
5. I feel the depression lift and the anxiety comes.  At this point, I am aware of what is going on.  I see the high and low.  But just because I am aware, does not mean I can control it.

Why isn't this bipolar? 
Good question.

Next topic:  is it Bipolar or depression?