Who said "A man is his own most dangerous enemy."?

This quote is attributed to Horace.

A man is his own most dangerous enemy. - Horace

"A man is his own most dangerous enemy."

Horace

Poet Ancient Rome 65–8

"Carpe diem, quam minimum credula postero."

"Seize the day, put no trust in the morrow."

"I have often regretted my speech, never my silence."

"Life gives nothing to mortals without hard work."