Three passes, in this order. Pass one: cut. Any sentence that could appear in someone else's vows, delete it. Generic lines are filler.
Pass two: specify. Every place you wrote something abstract, swap in a detail. "You take care of me" becomes "you put the electric blanket on twenty minutes before I get into bed."
Pass three: sound. Read it aloud one more time and fix the rhythm. Short sentence after a long one. Land the final line so it can be said in one breath.
And now the secret sauce, which is embarrassingly simple: practice out loud, at least five times, standing up. Not in your head. Out loud. It's the single difference between people who get through their vows and people who can't.
Then print a copy on a small card and put it in your pocket on the day. Even if you never look at it, knowing it's there is what lets you look up.