All of us have an optimal time of day for high performance and creative thought. We can look to an interview with Teresa Amabile who studied workplace stress for ten years. While many of us see stress as a stimulant to keep us moving through the day, the data speaks to the contrary:

"Perhaps the most surprising finding from the time pressure study is
that time pressure really does seem to have an important impact on
creativity, even though our intuitions are contradictory and previous
research is inconclusive."

In order to stay productive, try single-tasking instead of multitasking. Tim Ferris has written extensively on this and offers some practical tips on how to do one thing at a time.

Another strategy for keeping on your game is to repeat (i.e. mantra) phrases to yourself during the day. These should be simple, to the point and meaningful to you. Just because someone else said it, doesn't mean that it's going to work for you. Here are some suggestions:

I am good at what I do

Fast, smart, thoughtful

My focus is on those I serve

What's my next step?

One thing at a time