Poetry Meter by Meter

I'm not as proficient as I could be. Are we ever? Everyday I discover pieces to a gigantic puzzle whose picture is still unknown to me. I suspect I'd be bored with a box-illustration of my life's adventure. Finding pieces under rugs and in book bindings and wise words - a more riveting quest. Today, I discovered just how naive my knowledge of poetic metric stands. I remember as a child struggling with syllables and stress on words. I always suspected I could stress any portion of a word depending on its placement and purpose. While this is technically true, I'd quickly sound like a fool abusing that principle.
I remember learning to clap as a child for each syllable. "Pancakes" -> *clap clap clap clap clap* 5 syllables. The more excited I get the more syllables a word contains? Fabulous! I've been reading poems, and sometimes it is obvious as in the Destruction of Sennacherib:
 The Assyrian came down like the wolf on the fold,
And his cohorts were gleaming in purple and gold;
And the sheen of their spears was like stars on the sea,
When the blue wave rolls nightly on deep Galilee.

And sometimes I struggle more finding a rhythm, or the rhythm varies for effect:
She walks in beauty, like the night
   Of cloudless climes and starry skies;
And all that’s best of dark and bright
   Meet in her aspect and her eyes;
Thus mellowed to that tender light
   Which heaven to gaudy day denies.

Reading these aloud, I feel a fight with some of the phrases. I want to emphasize certain parts, even though they are not stressed:
Meet in her aspect and her eyes -> / u u / u / u / is how it is supposed to be read, where sometimes I want to read it: u / u / u / / u
Or rarely :
u / / u u / / u
Both of which unstress the final syllable instead of stress it. Part of the problem is in the difference between this verse and all preceding metric. Each of the former lines are in iambic forms, and the fourth switches things up by starting out stressed? Tricky tricky, Lord Byron.

Then there are these:
Nor law nor duty bade me fight,
Nor public men, nor cheering crowds.
A lonely impulse of delight
Drove to this tumult in the clouds.

It starts out in iambic tetrameter, and finishes with a trochee and more iambic verse? That trochee so tricky! I see what you've done Yeats. Or do I? Such simple but effective techniques to alter the audience's perception and flow, focusing them or distracting them for significant, and subtle, purpose. Oh, to be a poet meister.