Can a journal article contain a personal circumstance description as motive for justifying the literature approach? I was recently invited to have a paper published. 

Unfortunately, a similar paper is about to be published on the practical/fun aspect of the project so I've had to re-frame the topic to focus on what we understand about the need for the project rather than the fun stuff itself.

The new paper required discussion on some aspects of psychology. I need to justify why I, as someone not in the field of psychology, felt capable of identifying it as a subject relevant to the discussion and presumably why I have slightly more than a fleeting grasp of the concepts. The gist is a long history of interacting with professionals on what defines my mental processes.

What would be the best way to say the discussion is best accompanied by an overview of the side subjects?
If you submit the article to a peer-reviewed journal, the reviewers should not (be able to) look at your academic history or status. If it gets accepted, the fact that it has been accepted shows that people think the findings are relevant for the field. There is no need to defend yourself in the text.

Furthermore, I would avoid any personal statements, especially if it concerns your own mental health, as it may jeopardise your career in the future.