Repetition of keywords and phrases

By repeating keywords and phrases, you can create a powerful cohesive effect. Be careful, though; too much repetition can create a ludicrous effect.
Of course, repetition isn’t desirable. However, if it is used correctly, it will make your prose more interesting. The key is finding that word or phrase that is crucial for the reader’s comprehension of the passage. By repeating this word / phrase, you can leave a powerful impact on the reader. Just make sure that you do not overdo it.
Read the sentence given below. It is a quote from Abraham Lincoln.

‘You can fool some of the people all of the time, and all of the people some of the time, but you cannot fool all of the people all of the time.’

This sentence is a classic example of the power of repetition.
Repetition can be employed to connect both sentences and paragraphs.

Pronoun reference

Pronouns avoid the repetition of ideas. They connect ideas because they almost always refer to a noun or noun phrase in the previous sentence.
You can use a pronoun to refer to a noun. The pronouns this, that, these and those can be used to refer to entire sentences.
Make sure that all pronouns have clear references. This is necessary to avoid ambiguity.

Parallelism

Parallelism is the deliberate repetition of phrases or even clauses of the same kind. This is a powerful technique. Inexperienced writers often assume that they cannot repeat the same phrase or clause structures. But that is a wrong assumption. Parallelism within the sentence is highly desirable.
Vary the sentence patterns. For example, you should consider writing a compound sentence after a complex sentence or simple sentence. You should use different types of linking words. All of these techniques add variety to your writing. You must still ensure that every sentence you write has a parallel structure.