UNITY

  Unity is that property of style which keeps all parts of a sentence in connection with the principal thought and logically subordinate to it. A sentence may be constructed as to suggest the idea of oneness to the mind, or it may be so loosely put together as to produce a confused and indefinite impression. Ideas that have but little connection should be expressed in separate sentences, and not crowded into one.

  Keep long parentheses out of the middle of your sentences and when you have apparently brought your sentences to a close don't try to continue the thought or idea by adding supplementary clauses.