Charles Spurgeon said the following in sermon #537 delivered on October 18, 1863:
Labor is light to a man of cheerful spirit!
You can work all day and almost all night, when the spirits are right. But once let the heart sink and your soul lack encouragement, and then you grow weary, and cry, “Would God it were evening, and the shadows were drawn out, that we might rest from our toil.”
Success waits upon cheerfulness.
The man who toils, rejoicing in his God, believing with all his heart, has success guaranteed.
He who sows in hope shall reap in joy.
He who trusts in the Lord and laughs at impossibilities, shall soon find that there are no impossibilities to laugh at, for to the man who is confident in Jehovah, all things are possible. It is thus of paramount importance that the spirits of the Christian should be constantly kept up.