What is the moral lesson about portrait of a great man?

It's impossible to say definitively what the "moral lesson" of "Portrait of a Great Man" is without knowing which work you're referring to. There are many artistic and literary works with that title, each with its own themes and messages.

To help me understand which work you're interested in, could you please provide more context? For example, tell me:

* Is it a painting, a novel, a poem, or something else?

* Who is the artist or author?

* What is the general plot or subject matter of the work?

Once I have this information, I can better understand the work and help you identify its moral lesson.