100% happiness is not possible?

[PavSalco]

I've got every relationship on 100% (fame as well), yet my overall happiness doesn't surpass 99%. What's necessary to make it full? Am I supposed to buy every item from the shop?

[Pascalimero]

I had the same question once, but I was able to achieve 100% happiness in my 3rd season.
There was no specific event related to this achievement.
I believe there is a hint in the game that you also need to be succeful, famous, play well, etc.