Jataka Story Request: Mindfulness, Radiant Complexion and Grass Simile

I'm looking for a story in the Jataka wherein the Buddha talks about mindfulness and the importance of not living in the past or future. He compares the mind living in the past or future to grass that has been cut off from its root. When that happens the grass will dry out and the same thing happens to the mind that does not live in the present moment. It was asked how monks who only eat 1 meal a day or sometimes don't eat at all can still retain such radiant complexion. That's where the Buddha taught the above grass simile. *Here's a link to the video where Bhante talks about it. It's mentioned at 6:45 into the video.* Can anyone help me find the Jataka story? Thank you for your time.