"You say, "If I had a little more I should be very satisfied.' You make a mistake. If you are not content with what you have, you would not be satisfied if it were doubled." (Source)
I heard someone say that if a person cannot live on $500 a month, they would not be able to live on $5000 a month - except, that if they made $5000 a month their problems would be a lot greater than if they only made $500 a month!
Recommended reading:
The Forgotten Spurgeon, by Iain Murray
A Defense of Calvinism - by Charles Spurgeon