As authors, of course we have to revise our stories. It's a very rare--if even existent--talent to be able to write a flawless first draft that's publishable.
There are many different methods for revision. Some people use beta readers and critique partners to help pinpoint the problems in a story and then take that feedback as they work on each subsequent draft. Some hire freelance editors to do the same thing. Some, like me, just go it alone, using feedback on previous books as a guideline. Personally, when I revise I try to take off my author hat and put on my editor hat, and then I go through again wearing my reader hat. Not always an easy process.
The thing about being an author is sometimes we see flaws in our writing that aren't really there, or that aren't as much of a problem as we think. While it's definitely important to revise so we can submit the best possible manuscript, it's also important to know when to stop revising and just hit send.
Otherwise, we could revise until the end of time and never submit a single book.