Giving it all you got daily can be challenging. There are some days when faking it until you make it is the best you can do. I understand that doing your best is important and, in some occupations, you cannot have an off day.
All I am saying is that being human comes with boundaries and limitations that sometimes cannot be overcome. Doing the best, you can does not always mean 100% effort, often it means something closer to 50%.
I guess it depends on your attitude or how you are feeling physically and mentally. Circumstances can also dictate what doing your best really means. Expectations and reality are two different things here and how you approach what life throws at you and how you meet those challenges. Do your best, whatever that looks like and then let it go. There is only so much one person can do in this life.