Why is Sysyphus happy?

Hi All,

I have been confused by the core notion of the book the myth of sysyphus.

If I were pushing a stone up a mountain, I'd be tired and bored and in pain. Sure, I can feel free from the illusion that there were any intrinsic meaning to life anyway, but why would I be happy? To me, freedom doesn't necessarily equate to happiness.

Can someone help answer? Thanks.