How to overcome fear when waking up in the astral?

From time to time I "wake up" in the astral (i.e. while outside of my physical
body, in the dream state) but the experience is always so *weird* that it
frightens me. Invariably the experience of this fright causes me to hie it back
to my physical body as fast as possible, sometimes even at the cost of great
effort!

For example, early this morning I was lying (in my astral body) in a bed in a
pleasant room with a curtained picture window on one side. The bed was next to
the window and I was lying with my back to the window. At the same time, I was
somehow aware that my physical body was lying in a different, but quite similar
room, also with a curtained picture window, in a very different bed, but also
with my back to the window. In both scenes, astral and physical, I was lying in
a bed with my back to a window, and snoozing. Suddenly there's a loud knock on
the window! I'm frozen with fear and can't move. Frantically I try to turn my
body over to look at the window, but I cannot. After huge efforts, I am able to
turn over, but of course find myself back in the physical body. Some rain drops
are falling on the parapet outside, making gentle noises.

I immediately realize what happened - the knocking was in the astral scene, a
signal to "wake up" there, and it *did* wake me up there, but I was so startled
and scared that I instinctively ran back to my physical body.

I guess this kind of thing happens to everyone? But how to stay calm, stay put and not
run back?