Self-citation is acceptable whenever is necessary, especially for the related work. But it should not be a strange habit such as citing 20 papers at the same time if 10% of your references is from your relevant papers should be no problem.

Dear Esmat,

See the link below:

https://www.researchgate.net/post/Is_self-citation_good_for_showing_the_continuity_of_the_research_and_avoiding_self_plagiarism_Please_share_your_experience_and_thought

Self-citation is acceptable whenever is necessary, especially for the related work. But it should not be a strange habit such as citing 20 papers at the same time if 10% of your references is from your relevant papers should be no problem.

Dear Dibakar,  Thank you for the new prospective...  I never saw it this way...  Regards

Thank you Dear Hadeel for sharing that post...  I read most of the answers... It is really comprehensive and mind opening..  Warmest regards

Dear Gomaa,  thank you for the mentioned percentage...  & I do agree with you that self citation must controlled by relevance and decency.. Best regards

It is not good 

Dear @Esmat 

This % is based on my experience and my own view. I mean it is not standard or established value.

For example, in the following Q1 paper, I cited 9 papers of mine out of 50 references. But all of them are relevant.

High performance MnO2 nanoflower supercapacitor electrode by electrochemical recycling of spent batteries

http://www.sciencedirect.com/science/article/pii/S0272884217305849#bibliog0005

Dear Neelamadhab...  Thank you for sharing your opinion.. Regards

Thank you Dear. Gomaa, your valuable opinion is highly appreciated...  As you said,  since there is noestablished value...  It is all about personal experiences...  Regards 

When the previous work was important and related to the new project it is good but you should not cite your papers to increase your citation .

In general, moderate amount of self-citation is often inevitable. But excessive self-citation can be considered rather crass and unprofessional, and in some cases is unethical.  Anyhow, in some cases, self-citation (even excessive self-citation) may be valid and forgivable. For example, if you are in a restricted field of research, self-citation may be unavoidable. If less than half a dozen scientists study your species or region, you’ll quickly find that you are citing each other repeatedly. Also, PhD students are expected to produce publishable works from dissertation chapters, so these publications will be linked. Self-citation is therefore inevitable in this situation, especially if post-doctoral work follows on from PhD studies. Anyhow, it is a common rookie mistake by young, ambitious academics to excessively self-cite grey literature.

In my openion self-citation is acceptable if it is relevent to the topic and reflect the continuity of the previous research. However, unnecessary self-citation are extremely not acceptable.

Esmat Wahdain

Generally, to assure an accurate practice, self-citations should be used to support the arguments, not to demonstrate your research. Moreover, self-cites may used to compare recent findings of the research with previous results when studying the same theme. The important point here is to avoid turning self-citations into self-promotion.