“In each century since the beginning of the world wonderful things have been discovered….In this new century hundreds of things still more astounding will be brought to light. At first people refuse to believe that a strange new thing can be done, then they begin to hope it can be done, then they see it can be done, then it is done and all the world wonders why it was not done centuries ago.
One of the new things people began to find out in the last century was that thoughts, just mere thoughts, are as powerful as electric batteries, as good for one as sunlight is, or as bad for one as poison. To let a sad thought or a bad one get into your mind is as dangerous as letting a scarlet fever germ get into your body. If you let it stay there after it has got in, you may never get over it as long as you live.
So long as Mistress Mary’s mind was full of disagreeable thoughts about her dislikes and sour opinions of people and her determination not to be pleased by or interested in anything, she was a yellow-faced, sickly, bored and wretched child.
When her mind gradually filled itself with robins, and moorland cottages crowded with children, with queer crabbed old gardeners and common little Yorkshire housemaids, with springtime and with secret gardens coming alive day, by day, and also with a moor boy and his ‘creatures’, there was no room left for the disagreeable thoughts which affected her liver and her digestion and made her yellow and tired.“
~”The Secret Garden” by Frances Hodgson Burnett (published 1911)