There's good and bad kinds of repetition.
Some writers, even published, end up leaning on crutch words. These are uncommon or jarring words that the author has a bit of a secret love affair with and soon stick out like sore thumbs in the prose - things like 'zesty' being one of the worse offenders. It's a good idea to check through your writing to make sure you're not leaning on something.
There's also repetition of pronouns or sentence beginnings, the classic example being when someone writes a paragraph like this:
I put my shoes on. I left the house. I walked down the street. I looked both ways as I crossed the road. I didn't see the car coming. I fail at life and varying the beginnings of my sentences.
All different words and phrases can cluster your prose with repetition. A good site to use when revising is simply wordcounter.com to see if something is amiss. The results can be suprising. [I used 'dark' 22 times on the same page??!]
Good repetition in my eyes is where it's used sparsely for effect: In. Out. In. Out.
...okay I was thinking of breathing control, but that sounded dirty.
Another thing is circulation, which is repetition in a sense - where the beginning and end of a story connect. This can be very effective. Personally, circulation does not come naturally to me so I don't use it much. I definitely don't deny its power though.