Those who abide in the forest,
Peaceful, living the holy life:
Those who eat but a single meal:
--why is it their face is so calm?
Then The Buddha gave answer to him:
They do not grieve over the past,
Nor do they yearn for the future:
They live only in the present
--That is why their face is so calm.
It's from yearning for the future,
And from grieving over the past:
This is how fools become withered
--Like a fresh reed that's been hacked down.
(Aranna Sutta: SN 1. 10)