Someone had asked me about this phrase yesterday. Why the Monday morning blues?
Here is the answer...
For everyone who works the typical Monday through Friday schedule, Monday is always the worst, and Monday morning is the worst part of Monday. Why? It is because these people have to drag themselves up from their bed and they find it hard, especially if they have had a fantastic Sunday night partying or just came back from a short trip over the weekends. Thus, these are the reasons why they dread it, they fear it, and some people hate their Monday morning.