I want you to remember that big words do not always equal good writing.
Check out Charles Bukowski or Billy Collins, for example. They write using very simple words and stanzas, yet their poems still contain complex themes and are very thought-provoking.
My advice? Make a list of your favorite words, the “biggest,” most beautiful words you can think of, and then keep that list for reference.
Every time you write a poem or prose piece, try to fit a few words from your list into it. But don’t make the words seem forced; don’t just toss them haphazardly into your poem or prose just for the sake of adding a few “big words.” Instead, incorporate them smoothly so that the poem or prose piece still has a natural flow.
I hope that helped! :)