It's the kind of happiness you feel when you're around somebody you love. You have no reason to smile, but you just do. To know that you have actually found somebody you can completely surrender to, to know they they're willing to accept you, and support you; flaws and all. It makes you smile for no reason. It feels like a thick blanket in a freezing cold room, while it's raining outside. Nice, isn't it?
Like when you play with a dog. Dogs are so happy when you just give up a few moments of your time for them. When they lick you on the face because they love you for just sharing a minute, that's a good feeling. Like how a cat purrs just because you've been stroking it for a few seconds. Or just because you scratched it in the correct place.
And that feeling, of simple joy.. it's just pure happiness. No splendour, nothing material. Just happiness in its original state. It's just happiness. And it's amazing.