When you are relaxed, in the flow and expect great things, you not only enjoy the ride but find things fall into place.
You have an built-in mechanism that can deal with enormous things. However, when you get unnecessarily worked up, a lot of your energy goes to waste.
So if you are having a very busy day with lots to do, take a deep breath, get organized, and deal with your priorities one at a time in a relaxed and confident manner.
Your demeanor will dictate your approach.