Those who laugh harder aren't really sad inside. Here's why:

I randomly see post saying that the saddest people are those that usually laugh harder or make the most effort to make someone happy.

Well, this isn't true as much as you want it to be true. They laugh harder and have external disposition of happiness because inside them reverberates its abundance. Its hard to give laugh when in inside it deficits. You cannot give what you dont have. So next time if you notice someone eject a happy state its because they have a lot of it internally. And their happy to share it with another person whose lacking. That's simple at is it.