You need to get used to the idea that your first draft will suck. Most first drafts suck. Let it be a blog post, an essay, or even a book that you spent years writing, the first unedited (or lightly edited) version is going to be terrible.
That's a matter of fact.
The fastest you accept it the fastest you can leave worrying about quality behind to actually write. There will be time later to improve it.
Good writing doesn't come out like that on its own. You can archive good writing through great editing.
What can you do?
The best thing would be to hire an editor and almost every professional blogger does so. If you're only a hobbyist like me though, the expense of hiring an editor can't be justified.
1. Use Grammarly to check for misspellings
Grammarly will not only check for spelling errors but also check your punctuation and grammar.
2. Read your article out loud or use a text to speech application.
Mostly to see if your article flows well as a unit. It is especially useful if you're writing dialogue or long form articles.
3. Let someone else proofread it
After you read your writing multiple times you become familiar with it and you will notice mistakes way less than someone that has a fresh view on it.