What is the English equivalent of "nguyên tắc"?

Give the synonym of "defeat"?

Young children should not be left by themselves.

We all supposed him to be German, but in fact he was Swiss.

After the accident he lost his ___________ for the sport.

I __________ the memories of the time we spent together.

Give the Vietnamese equivalent of "pasture"

He's always meddling in (= trying to influence) other people's affairs.

Give the Vietnamese meaning of "personality"