To be worried, you would have to be comparing right now with another time. And the past and the future don't even exist! Worry is all about imagining an unwanted scenario and then believing it will happen!
Mr.Nut tells me that squirrels never do this... in fact, they can't even imagine anything other than what is happening right now! Plus, they are so busy enjoying what is happening every moment, that they can only be grateful!
The saying goes, 'The sage (squirrel) rests, truly rests and is at ease.' This manifests itself in calmness and detachment, so that worries and distress cannot affect him, nothing unpleasant can disturb him, his Virtue is complete and his spirit is not stirred up. ~Chuang Tzu