。
Caution is the better part of valor.
Literal
Caution [topic-は] courage [possessive-の] major-portion.
A direct rendering of the English proverb. The noun 用心 ('caution / wariness') stands as the bare topic, and the predicate 大半 ('major portion / most of') is delivered without any copula — a classic proverb-style ellipsis that compresses the assertion. 大半 itself is a Sino-Japanese compound 大 ('large') + 半 ('half').