It is more likely you've written too much than too little.
The rule for most writers is, "If in doubt, cut it." If a word, sentence, or paragraph isn't necessary, delete it. It will clarify what you're trying to say.

• A recommended how-to guide on writing good, clear English is “The Elements of Style” by William Strunk Jr. and E.B. White.

• “Politics and the English Language” by George Orwell is also worth studying to avoid “ugly and inaccurate” writing.
• A writing ass...

When you write something, you get very close to it. It is nearly impossible to distance yourself from it straight away to edit properly.

Most writing mistakes are widespread, but good writers just get better at spotting them. Some things you'll learn to watch for are:

The structure is what your writing hangs on. 

The beginning of anything you write is the most important part. If you don't catch someone's attention at the start, you won't hold it later.