I love Mondays. Really, I do.
Almost without exception, I exercise on Mondays.
No matter what your exercise participation status might be, try doing something physical today. If you can, do it before your work day starts.
If doing such a thing is new for you, make sure that you keep yourself safe (nothing too intense or unfamiliar) and that you manage your time appropriately. These will help to ensure that the experience is as positive for you as possible.
In my experience, weeks that start like this are just better.
Find out for yourself.