Using your own work and academic integrity:
If you chose to use your own work in another work, it must be cited like any other. Just because you wrote it yourself, does not mean you cannot plagiarize.
If you're published with a publisher, you should first check your publishing agreement because it might specify the format of the citation. If your publishing agreement does not specify, please use a standard citation (APA, MLA, etc.). Not citing a work, even if it is your own, is a form of plagiarism that is unacceptable in academia.
This is a serious issue and you can expect it to be treated with the gravity of any other issue concerning academic integrity.