Mixed Constructions in Sentences

I know I just did this in class today, but when I write things down and put them in a place that I look often, I remember them. The question is what are mixed constructions? Sentences that change structures midway through, and they don't logically fit well together. I have a problem with this because I will often start writing with no purpose. I start a sentence with one idea and end it with another. This is a habit I need to break. In a tutorial about mixed constructions by Bedford/St. Martin's it helps us get a better understanding of these sentences. From this article there are three things they suggest you do; make sure phrases or clauses work well together, make subjects and predicates consistent or agree, and avoid the constructions; is when, is where, the reason is....because. The follow are some examples that can help us better understand.

Make phases or clauses work:

Wrong: The fact that the marathon is twenty-six miles, a length that explains why I never have finished it.

This sentence starts out with an independent clause (the fact) which is followed by a dependent clause (that the marathon is twenty-six miles). All this sentence needed was a predicate to make it complete, but instead it added another noun (a length) and dependent clause (that explains why I never finished it).

Corrected: The marathon is twenty-six miles, which is why I never have finished it.

Subject Predicate Agreement:

Wrong: The most valued trait in an employee is a person who is loyal.

The reason why this doesn't work is because a person cannot be a trait. The way it reads right now is saying that it is.

Correct: The most valued trait in an employee is loyalty.

Avoiding is when, is where, the reason is....because:

Wrong: Indigestion is when you cannot digest food.

You are using is when.

Correct: Indigestion is the inability to digest food.

As you fix this sentences they become easier to read, and less confusing.