Show or tell: what is it when it's at home?

[busker]

I would like to know people's thoughts on this frequently brought up angle in many critiques.

I am frankly often confused by the difference.  That is, I have hard time sometimes seeing the dividing line.  It seems like every poem is a telling.  I do understand the importance of showing, since images are sort of the blood of poetry.  

Maybe I'm the only person who doesn't quite get it.  Analysis is not one of my strong points.

Anyway, enlighten me!

Telling would be bland narration.
Anything that doesn't tease the mind, fire the neurons.
Showing is painting a picture, but of course not all poems paint pictures. Some of focus on the sonics. Some of them tease the mind differently.

Is the following telling?

Old men ought to be explorers
Here and there does not matter
We must be still and still moving
Into another intensity

None of the above is bland narration. The first line is intriguing, the third is clever ('still', and 'still moving'. Moving by being still. Focusing the mind. Moving with the mind.) The last line is mysterious again. Another intensity? What would that be like?
But none of them paint a picture.
Then we have the next line, also not painting a picture, but teasing the mind:

For a further union, a deeper communion

Then finally we have something inexplicably wondrous, like the universe just exploded. The petrel and the porpoise, with their endless allusions, both obvious and subtle, both intended by the writer and imagined by the reader. This would be properly showing, the 'vast' makes it so. And the last not-telling line rounds it out.

Through the dark cold and empty desolation,
The wave cry, the wind cry, the vast waters
Of the petrel and the porpoise. In my end is my beginning.