For example, in this sentence a pronoun should have been used:
The desire people have to nurture their dogs arises from human tendency to identify with their dogs.
The second half of the sentence should read: "...from the common tendency to identify with them."
Repetition may also refer to ideas that you have used more than once or to sentences that are rewrites of previous ones. Make sure your essays move forward with each sentence and do not belabor your points.