get out of bed the wrong side

get out of bed the wrong side

or

get out of bed on the wrong side

If someone got out of bed the wrong side, they are in a bad mood all day and there is no obvious reason for it. Sorry I was so grumpy when I arrived this morning. I must have got out of bed the wrong side. Note: This relates to the old superstition that it was unlucky to put your left foot on the ground first when getting out of bed. `Get off on the wrong foot' is based on a similar belief.
See also: bed, get, of, out, side, wrong