It's good to provide empathy to people who are struggling.
John is talking with Susan when Susan tells John that she is feeling depressed.
John wants to respond to Susan's statement about depression.
John tells Susan that he's sure it's tough and that he's there for her if she needs him.
John tells Susan to just suck it up and cheer up already, that it can't really be that bad.
Susan feels supported and is glad John is understanding, so she feels a tiny bit better as hard as it is.
Susan feels isolated and lonely because John doesn't understand what she's going through.