Looking for a Metaphor

I thought
for a long time
that I was a catalyst.
I was there to speed up
and sometimes start
my students and their thinking.
A catalyst in chemical reactions
does that.
And I was proud of my metaphor.
Until...
Not being a science teacher,
I discovered my understanding
of a catalyst was flawed.
A catalyst does indeed start
and/or speed up a chemical reaction--
but in doing so,
it remains unchanged.
And after twenty-eight years of teaching
there is one thing I am sure of...
teaching all these kids has changed me.
So I think I need a different metaphor--
I am not the same person
who started this ride so long ago.
I am different in ways both good and bad
but there is no way
I could do this
and remain
unaffected.

©2015-Art Belliveau