Completion is such a big thing for everybody these days. There's a misconception that people who're truly happy can't be incomplete, since the lack of something important within the wholeness of the self can't constitute to being happy.
People are likening happiness to stew. You can't get a good stew going without a good base.
Now, I've never been the happiest man alive. In fact, when it comes to the level of happiness anybody can have, I'm probably the dude who's sitting in the aisle, trying to figure out what question number fifteen was about. But there's one thing I've learned about being happy, and that's people are never happy by default. Not with everything we have to put up with. People and things can make us happy for the time being, but in the end, the way we think and figure things out for ourselves is what's important.
So yeah; in a way, the only people responsible for our happiness is ourselves. Which isn't a very comforting thought, especially for people like me who have a hard time trying to keep ourselves in a jovial mood for very long in the first place.
But still. I think this calls for a bit of re-evaluation. Think of being happy as a bunch of Lego blocks. Each individual block is complete, despite the fact that there are holes underneath it that could use some support, or that there are spots above it that could support other people. The fact that it's a complete Lego makes it whole; the fact that it lacks some parts and can support other parts means that as a Lego, it has achieved Nirvana - it just doesn't know it yet.
We're people. We're the same. We can't ever be complete, because people were created with flaws to add to the character of each individual. And that's more than enough reason to be happy - because we can.