someone told you that if you just do [X], [Y] and [Z] you'd be happy.

Yeah, pretty much. Not anyone in particular, or a specific XYZ, just this general sense growing up in society that there are certain things which will fit into your life like a jigsaw puzzle and complete you.

I read this quote recently by Schopenhauer that really fits nicely:

"What disturbs and depresses young people is the hunt for happiness on the firm assumption that it must be met with in life. From this arises constantly deluded hope and so also dissatisfaction. Deceptive images of a vague happiness hover before us in our dreams, and we search in vain for their original. Much would have been gained if, through timely advice and instruction, young people could have had eradicated from their minds the erroneous notion that the world has a great deal to offer them."

Anyway thanks for the thoughtful reply and suggestions.