The wrong side of the bed

Mother Superior was on her way to late morning prayers, when she passed two novices just leaving early morning prayers, on their way to classes. As she passed the young ladies, Mother Superior said, 'Good morning, ladies.'
The novices replied, 'Good morning, Mother Superior, may God be with you.'
But after they had passed, Mother Superior heard one say to the other, 'I think she got out of the wrong side of the bed this morning.'
This startled Mother Superior, but she chose not to pursue the issue.

A little further down the hall, Mother Superior passed two of the Sisters who had been teaching at the convent for several years. She greeted them with, 'Good morning, Sister Martha, Sister Jessica, may God give you wisdom for our students today.'
'Good morning, Mother Superior. Thank you, and may God be with you.'
But again, after passing, Mother Superior overheard, 'She got out of the wrong side of bed today.'

Baffled, she started to wonder if she had spoken harshly, or with an irritated look on her face. She vowed to be more pleasant. Looking down the hall, Mother Superior saw retired Sister Mary approaching, step by step, with her walker. As Sister Mary was rather deaf, Mother Superior had plenty of time to arrange a pleasant smile on her face, before greeting Sister Mary.
'Good morning, Sister Mary. I'm so happy to see you up and about. I pray God watches over you today, and grants you a wonderful day.'
'Ah, Good morning, Mother Superior, and thank you. I see you got up on the wrong side of bed this morning.'
Mother Superior was floored!
'Sister Mary, what have I done wrong? I have tried to be pleasant, but three times already today, people have said that about me.'
Sister Mary stopped her walker, and looked Mother Superior in the face.
'Oh, don't take it personally, Mother Superior. It's just that you're wearing Father Murphy's slippers!!' 

Thanks to MadPriest!