To see what I mean, check out this letter he wrote to To Charles Lyell on October 1st, 1861.. Towards the bottom of it he comments:
But I am very poorly today & very stupid & hate everybody & everything. One lives only to make blunders.
Sounds familiar to anyone having a bad day. If you are having one right now, maybe do what Darwin would do and go for a walk. It can’t hurt!
Smart People I Know 
A good walk is always a great thing.
Agreed!