a leopard cannot change its spots; the child is father to the man
Proverb meaning that one's fundamental character, formed in early childhood, remains unchanged throughout life. Literally: 'the soul of a three-year-old (stays the same) until one hundred.'
He's still short-tempered even as an adult. They really say it well: the child is father to the man.
As the saying goes, a leopard cannot change its spots; her meticulous nature hasn't changed since she was a child.
A traditional Japanese proverb. The exact origin is uncertain, but it reflects the folk belief that personality is largely fixed by early childhood.