Elegant Variation

The phrase, Elegant Variation, was coined by Henry W. Fowler in The King's English (1906). The essence of that term will help Indian writers to understand how carefully one should write. 

"...The use of pronouns is itself a form of variation, designed to avoid ungainly repetition; and we are only going one step further when, instead of either the original noun or the pronoun, we use some new equivalent..."

Fowler then lays down two guidelines:
"...It is impossible to lay down hard and fast rules, but two general principles may be suggested: (1) Variation should take place only when there is some awkwardness, such as ambiguity or noticeable monotony, in the word avoided. (2) The substitute should be of a purely pronominal character, a substitute and nothing more; there should be no killing of two birds with one stone."

Try to practice it. It is very interesting.