I have heard that a gentleman said to a Negro, “I can’t think how it is you are always so happy in the Lord and I am often downcast.” “Why Massa,” said he, “I throw myself flat down on the promise—there I lie; you stand on the promise—you have a little to do with it, and down you go when the wind comes, and then you cry, ‘Oh! I am down;’ whereas I go flat on the promise at once, and that is why I fear no fall.” Then let us always say, “Lord there is the promise; it is thy business to fulfill it.” Down I go on the promise flat! no standing up for me. That is where you should go—prostrate on the promise; and remember, every promise is a rock, an unchanging thing. Therefore, at his feet cast yourself, and rest there forever.
From a sermon delivered on Sabbath Morning, January 7th, 1855, by the REV. C. H. Spurgeon
You may read the full sermon here