This site is possibly a duplicate of Cognitive Sciences.
The Cognitive Sciences StackExchange was formed by merging previous "Psychology", "Psychiatry", and "Cognitive Science" proposals.
Scientific questions about psychology are on topic at the Cognitive Sciences Stack Exchange. In fact, such questions form the vast majority of the site.
There has long been discussion in meta on Cognitive Sciences about the degree to which the name of the site could be made more inviting, particularly to scientists in the field of psychology. That said, questions relating to the science of psychology are on topic.
Self-help questions are off topic for various reasons.
See my question "How can I help my bipolar friend?". Cognitive sciences may investigate how human sensation, cognition and information proccessing work but I think that personal advice, situation analysis, personal managment (HR) and understanding the human behavior in general is not a field of interest of cognitive sciences.
Look the new questions for better definition, psychology should be the main-topic that can include so many variants.
These sites seem very different, in terms of content, purpose, and user base.
"Cognitive science" takes an intellectual/scientific/occasionally-pop-sci approach to "how do human minds work in general". Examples: "Any work being done on Perception, Action, and/or Cognition in Video games?" "What are popular rationalist responses to Tversky & Shafir?" "How is it that taking a break from a problem sometimes allows you to figure out the answer?"
"Psychology" is about clinical psychology and psychiatry. "Which ADHD medications help break hyperfocus?" "How can I help my bipolar friend?" "What's the recommended treatment for post-traumatic stress disorder?" "why beta blockers are effective for anxiety?"
Purpose: To make broad generalizations, Cognitive Science seems to be for people seeking knowledge useful for self improvement, or seeking to learn for learning's sake. Psychology is generally about clinical psychology and psychology, with a focus on mental health.
User base: Cognitive Science seems largely composed of motivated, educated individuals, most of whom are not mental health professionals. (It also appears to have a large overlap with the "rationalist" community.) Psychology seems largely composed of mental health professionals and people affected by mental health issues.
Caveat: "Abnormal-Psychology" is the 9th most popular tag. Mental health issues are sometimes discussed. See "Why is depression a diagnosable issue?" - the question is focused on "is this a thing in the first place?" and the discussion would play out very differently in the psychology SE. My personal litmus test: I would not be comfortable asking mental-health related questions there - the community seems built for other purposes.
In short: "Psychology" is focused on mental health, "Cognitive Science" generally is not.