Teaching a child gratitude rarely works as a formal lesson, with a child expected to sit and list things to be thankful for on command. It tends to take root more effectively through modelling: a parent noticing something good aloud, in an ordinary, unforced moment, so the child absorbs the habit by example rather than by instruction.
Asking specific questions helps more than asking a child to be grateful in general. A question like what was the best part of today invites a concrete memory, while a vague instruction to appreciate things more often produces a blank stare or a rushed, insincere answer just to move the conversation along.
The goal is not to produce a child who performs gratitude on cue, but one who has quietly built the habit of noticing good things as they happen, a habit that tends to stick far longer than anything explicitly taught as a lesson to be remembered later.