I can't give just ONE answer, but I'll limit to a couple of things.
My music.
Making people happy.
And things I wish I had would be that I didn't have schizo-affective disorder, and I wish My best friend were still alive.

I have most everything working to keep me happy and personality growing.

There is always one desire not completely fulfilled yet. Is a lover to follow each other to the end of the earth.?

The word ONE in all caps

I have pretty much everything I have wished for. What makes me happiest at this time when not enjoying my peace and quiet, are hugs and smiles from my little grandsons, 1 & 4 years old. So sweet!

My daughter makes me happy, and proud. She's a very bright, beautiful woman, and she loves her dad. I feel very fortunate to live near enough to see her and my son-in-law fairly often.

As for what's missing? Someone who wants to be with me and accepts me for who I am; and whose life I can enrich.

*Define "happy" I'm indifferent to just about everything. And what would I do differently if I were "happy"? It's a BS phrase!. If you could elaborate just a tad bit more - I might be able to answer the question but it's subjective at this point. I might be "happy" because the "enemy's" bomb didn't blow my butt off - doesn't mean that I am "happy" to be there. Please elaborate .

The ocean and wild birds make me happy.
I wish I had horses in my life again.