I agree with you that this may be an unusual view of looking at things, but I'm sure your doctor has a
good reason for it.
My thoughts about this though is that phenobarbital has some form of sedative effect and I think this was
intended by your doctor to help calm you down and prevent anxiety (though this is not the primary mode of
action of phenobarbital).
It is best to directly ask your doctor regarding this, since we can have different opinions and points of view
regarding the matter. It is also possible that he already has a good experience regarding this drug in
treating anxiety.
Regards.