It took me a very, very long time to stop feeling guilty for working 6hr shifts instead of 8hr shifts.
I work freelance, and while I could work for 8hr, I don't because I feel exhausted when I do. Even though I felt better when I worked less, I constantly felt guilty because I could earn more if I wasn't so “lazy”. I had this idea that if I worked any less than what everyone expects me to work, I am being a spoiled brat.
The matter of the fact is… I perform twice as good when I cut those two hours, I also have time to cook and to hit the gym which improves my mood and in turn, improves my performance the next day.
If you want to be healthy mentally and physically, if you want to feel fulfilled and satisfied when you finish work, then shorten your working time if you can.