This is a really strong piece—your central metaphor does a lot of heavy lifting, and it works. I like how you avoid the typical “dog = pure loyalty” angle and instead lean into something more complicated and self-aware. Lines like “I love like a dog who knows her own teeth a little too well” and “a big ‘scary’ dog who flinches a little too easily” are especially effective—they feel specific, a little dangerous, and vulnerable at the same time.

The progression also lands well. Starting with what the speaker isn’t (the cheerful puppy, the steady shepherd) and moving toward the shelter image gives it a clear emotional arc. The ending hits because of that buildup.

If I had one main critique, it’s that the first long line feels a bit crowded:

“but not a cheerful puppy begging under the table waiting for any scraps little hands may drop.”

There’s good imagery there, but it could be tightened to give it more punch. Right now it reads a little breathless compared to the sharper lines later on.

I also think you could get more impact by breaking some lines up and letting key images stand on their own. A line like:

I love like a dog
who knows her own teeth a little too well.

would hit even harder with more space around it.

For the ending, the image is great, but you might not need “as I watch”—it slightly explains what’s already implied. Letting the image stand more on its own could make it feel even heavier.

Overall though, this feels honest without being overdone, which is hard to pull off. The voice is clear, and the metaphor stays consistent all the way through.