The main force in man — is the power of the spirit.
Ведь главная сила в человеке — это сила духа.
Original text (Russian)
Variants
The main human strength is willpower.
Original text (Russian)
Quote text and notes from Wikiquote: Yuri Gagarin (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.