Paracelsus

No greater thing is created suddenly, any more than a bunch of grapes or a fig. If you tell me that you desire a fig, I answer you that there must be time. Let it first blossom, then bear fruit, then ripen.

Whole foods like grains and beans release their sugar very, very slowly because of the fiber in them, and they don't give you a sugar rush. They feed your cells as needed, and as a result, you have loads of stable energy that powers you through the day.