Ehhhh kind of bullshit? And then also dangerous.
If something that impacted your happiness is no longer around, why must that result in pain? IMO, the lack of a source of happiness should not result in pain (although it often does). Maybe if it's your last one, or otherwise reduces overall happiness to below threshold values, but I'd say that's a signal you need to diversify your portfolio.
AFAIK, I know far to many people who then also equate pain with happiness, for exactly this thinking. You can stab yourself with a pen. Does that make the pen meaningful, because it can cause you pain?
I'd say the pain of loss is a strong and significant signal that something impacted your happiness, but the happiness itself should the (only) significant signal. Everything else is nuance and seasoning.