Home. Home is where I live. Home is where I have invested most of my resources so that I have a place to crash, to be secure in, to have a context outside of the rest of the world. It's a place that I can define in my own terms, where I can indulge at least the illusion that within a limited space, I am in control of my environment, and my influence holds sway.
Heart. Heart is life, the promise of continuity and the promise that life is worth continuing. Heart is courage, the confidence to keep struggling on when times are tough, even if it means adapting temporarily or changing permanently behaviours and routines one has grown accustomed to. Heart is love because we aren't alone to fend for ourselves; it's comforting to know that others can't do without us either.
Horizon. Looking ahead to the future. The continuity that stems from from the heart needs a direction and a destination -- somewhere to go in a roughly forward direction 'cos we really hate it when we discover we've been walking in circles all along.
Having said that, I'm not all that clear what PM means by "the mountain has moved; we are waiting for the mouse to come out," with reference to making babies. I have no qualms about moving mountains, and my mouse is always ready to come out, "mouse" being a rather modest euphemism compared to "mountains". Guess he's being a conservative Asian gentleman speaking about such things.
As for the babies... well, Jojo's been regaling us with tales of her weekend spent with half-a-dozen of them. They wrecked her Home, they quailed her Heart and they gave her second and third thoughts about getting Horizontal ever again, lest she unwittingly contracts one for herself. Jojo is not alone in this sentiment.
PM has his work cut out for him. You could say he has his hands full, moving mountains: "Home, Heart, Horizon"