Are there any elements of the story which stick out? These may be continuity errors. This is your chance to fix them before publication.
For example, in Richelle Mead’s VAMPIRE ACADEMY series, there are a few continuity errors which cause the reader to pause and scratch their heads.
In book three of the series, SHADOW KISS, the character Jill is first introduced as an Air User but in the following books and in the BLOODLINES series, she is a Water User.
In the first book, VAMPIRE ACADEMY, Dimitri tells Rose that he only has two sisters, but in book four, BLOOD PROMISE, he has three.
I’m not picking on this author or this series, everyone makes mistakes. The point is to look for them before self-publication. The best way to do it is by reading your book from start to finish, just for the sheer pleasure of it.
The final step of battling PPP is to repeat the process. Read your book, or ask others to read it, until you are confident the prose flows. Congratulate yourself, author. You’ve conquered PPP.