The conventional English sentence is based on one or more clauses, each of which must have a subject (sometimes the implied "you") and a verb.

Incorrect: Saw the jacket.

Correct: I saw the jacket.

TIP: Do not repeat a subject, even for emphasis.

Incorrect: The movie that I saw it was long.

Correct: The movie that I saw was long.

For more information on writing Different Kinds of Sentences, see Book I, Ch. 3; Book II, Ch. 16; Book III, Ch. 14.