enervate

enervate \EN-ur-vayt\, transitive verb:

1. To deprive of vigor, force, or strength; to render feeble; to weaken.
2. To reduce the moral or mental vigor of.

Beatriz de Ahumada soldiered on to produce nine more children, a tour of duty that left her enervated and worn.
-- Cathleen Medwick, Teresa of Avila: The Progress of a Soul

In countries like India, Pakistan, Indonesia, Nigeria and Ghana I have always felt enervated by the slightest physical or mental exertion, whereas in the UK, France, Germany or the US I have always felt reinforced and stimulated by the temperate climate, not only during long stays, but even during brief travels.
-- David S. Landes, The Wealth and Poverty of Nations

The tendency of abstract thought . . . to enervate the will is one of the real dangers of the highest education.
-- Mark Pattison, Suggestions on Academical Organisation

The conquerors were enervated by luxury.
-- Edward Gibbon, The Decline and Fall of the Roman Empire

Enervate is from the past participle of Latin enervare, "to remove the sinews from, to weaken," from e-, ex-, "out of, from" + nervus, "sinew."