She will not repine at what is not to be remedied, nor debilitate her mind by dwelling on her own causes of discontent, instead of awakening it to the numerous sources of happiness, which by increasing the happiness of others incite it to activity.
"Anna St. Ives"
Thomas Holcroft
You should move quietly among your layers if you would have them thrive, as constant agitation and disquietude will surely debilitate them and reduce their flesh.
"Natural and Artificial Duck Culture"
James Rankin
A close watch should be made for vermin in the house and on the birds, and if lice or similar parasites are discovered, immediate action should be taken to destroy both the adults and the eggs, since these parasites will debilitate the flock and prevent their development and may seriously check their ability to lay.
"A Living from the Land"
William B. Duryee