How did your baby cope when you returned to work. Any problems?

My 4 month old cries hysterically if she's overtired and cannot comfort nurse. Tried everything but wants mom. I know she will get used to the sitter in due time ( she's watched her while I went shopping) but it hurts to know she's in agony and gives up when mom doesn't show to soothe her. What problems did you run into and how did you handle it?