Being aware that this is a problem is half the battle. Just double-check for accuracy and whenever you type something that could possibly be a mistake, make sure you get it right.
Furthermore, practice-practice-practice. I assume from your post that you are relatively wet behind the ears, and I would think effortless accuracy only comes with time and experience. I used to be inaccurate all the time and now it's like my brain is rewired.
And don't give up hope, or get stressed out! Nobody's perfect, and new employees or people new to a field are bound to make mistakes all the time, no matter what industry. You said things are going well, so it doesn't sound like you're getting written warnings from the editor.
