I heard this on Glennon Doyle's We Can Do Hard Things podcast. The episode was Life Hacks: Strategies to Suffer Less. I don't remember much from the episode, other than this sage advice.
What does this mean?
When you start your day, pick the one thing you are dreading the most, and do it first. It's not a productivity thing, but a removing dread from your day thing. It doesn't mean on Monday eat all the frogs. It doesn't eat 365 frogs today. Just the one that you are dreading. By eating the frog first, you remove yourself from the dread that comes with it. You can finish the rest of your day lighter and happier.
It's something I NEED TO DO on the daily, and haven't been great at lately. Procrastination feels so much better at first - but not at the end of the day - right?