That’s a quote from an old book - “The Joy of Photography”. 

Personally I find it to be extremely true on many levels. Especially the “Everything is boring if you are bored” part. 

When applied to portraiture it’s about liking the person you are taking a picture of. 

“People are strange when you are stranger, Faces look ugly when you’re alone” (Jim Morrison) 

One of the reasons I became specifically a portrait photographer is because I genuinely love people and because I am endlessly fascinated by them.
And yes - even if I don’t quite like a person in front of me for some reason, I try very hard to change that immediately, looking for something I find beautiful and interesting about them. And I don’t recall a single time when I couldn’t find something. People are beautiful.