Your best is changing all the time. Your best will depend on whether you are refreshed in the morning or tired at night. Your best will be different when you are happy as opposed to upset, or healthy as opposed to sick. Under any circumstances, simply do your best, and you will avoid self-judgment, self-abuse, and regret.
This quote has come to mind these past couple of days. I'm learning that I want to be able to do my best at all times. I would hate to come to a point in life where I would think that I hadn't done the best I could.
Doing one's best is tricky to differentiate from doing what one thinks one should do; perfectionist tendencies cloud what one's best actually looks like.