Thus we say:

You never know, which is why but you never know.

That is why and goes on to explain:

Understanding the Context

There is a subtle but important difference between the use of that and which in a.

I don't know why, but it seems to me that bob would sound a bit strange if he said, why is it that you have to get going? in that situation.

I know it originates from head shrinking, but it doesn't help me a lot to understand the etymology.

Why are psychiatrists called that?

Key Insights

Is it like my head is swollen [from anguish, misery, stress