Posted this once before but I really like the encouragement at the end of a working week which contained 10,000 things arising and passing away:

He has shown you what is good,  and what is required of you: To do justice, to love kindness, and to walk humbly with your God. Micah 6:8

Do not be daunted by the enormity of the world’s grief. 

Do justly, now.  Love mercy, now.  Walk humbly, now. 

You are not obligated to complete the work,

but neither are you free to abandon it.

The Talmud