What determines humanity?
This is a common theme in the Blade Runner universe and is strongly echoed in Blade Runner 2049. What Joshi is saying is that we all look for that thing in our our lives that gives us meaning, and determines our humanity.
One of the original writers of Blade runner, Hampton Fancher, who is also one of the main writers of Blade Runner 2049 has said in a recent interview with Sonia Shechet Epstein (Sloan):
Sonia Epstein: Discerning difference between replicants and humans is central to BLADE RUNNER. You said you’re not a science fiction person, but why are you interested in replicants and artificial intelligence?
Hampton Fancher: I am interested in what it is to be human as in humane, and how so much of our history is the opposite. The solution to that, to some degree, is empathy. We’re lost because of our inability to live within our empathetic impulses, but the contradictions are intriguing. That’s in BLADE RUNNER. Plus the idea of perfecting ourselves... .
-Museum of the Moving Image | Sloane Science & Film, 2017-09-29, 'Interview with Writer Hampton Fancher of Blade Runner', by Sonia Shechet Epstein
Throughout the film, K struggles to find his place, to find meaning in his meaningless life. Is he just a Replicant Blade Runner, or is there more to him?
This struggle is not limited to the likes of K. Every Blade runner feels this existential crisis, as does every Replicant.
Even Roy Batty struggled to find his place, even though he was 'perfect'; he still gouged his maker's eyes out, only to finally save Deckard's life and prove his 'humanity'.
This is reflected in the 'ask the dog' scene between K and Deckard; when K sees the dog, he asks Deckard if he's 'real', to which Deckard replies:
I dunno, ask him.
It doesn't matter in reality whether you're 'real' or not, it's what you do that defines you. This is what K ultimately ended up doing, showing his humanity by doing the most human thing to do
...die for a worthy cause
Joshi's statement to K is a precursor to his actions.