Yeah, ditto. Sometimes it's fine and other times I just feel 'awful' and it's a hard feeling to put your finger on - not dizzy, not tired, just 'awful'.
I think there might be a pscycological element to this, too. If I hypo at a bad time, of when I was tired and hoping to go to sleep etc, I get very cross with myself. I'm not sure whether the crossness causes the awfulness, or the awfulness causes the crossness!