What Separates Mental Illness vs Everyday Feelings?

This information comes from the DSM 5- which means it's very general. Talk to a doctor if you want advice specific to you and your needs, because I'm definitely not a doctor and this is definitely not medical advice.
Source:
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). doi.org/10.1176/appi.books.97...