。
'Sickness starts in the mind' — how well put, don't you think?
Literal
Sickness [topic-は] mind [from-から] [definitional-とは] well said [resultative-ものですね].
Built around the proverb 病は気から (やまいはきから, 'illness comes from one's mindset'). うまく言ったもの ('well put / aptly said') uses ものだ in its appreciative/emotional sense — marveling at how fitting the saying is. ですね invites agreement. とは marks the proverb as the topic being commented on. The proverb itself means that one's mental state affects physical health — a concept deeply embedded in Japanese health culture and connected to ideas about 気 (ki/chi, vital energy).