Childlike
Part of speech: adjective
Definition: innocent and trustful; credulous; artless of, like, or suitable for a child; meek; submissive
Example sentence: Never lose the childlike wonder. Show gratitude... Don't complain; just work harder... Never give up.
Naif
Part of speech: adjective
Definition: Naïve.
Part of speech: noun
Definition: One who is naïve.