1) Read it out loud to yourself. Have you missed words? Do you trip over anything? 2) Read it aloud to two or three people who are unfamiliar with your industry. You're looking or understanding and reaction. Ideally, you'll hear _ hey, do you do that? That's how you tell you've gone beyond examples of good cover letters and they're enthusiastic.
We will all go through writing a business letter at least once in our lifetime. It does not matter if you are an employee, an owner, a stay_at_home mom (or dad) that has her own business at home; we all have to go through writing it. It cannot be avoided!