I think it would be safe to say that, regardless of how healthy or unhealthy you are, you'd probably be happier if you were healthier.

It's not that you can't be happy while ill or in pain - just that, however happy you are, you'd almost certainly be more happy if you could reduce whatever illness and pain you have. And ill health has no compensating benefit that might make it worthwhile.

Neither health nor happiness is a binary, but surely there is at least a weak link between them.