Personally, i was happy when i was blinded to TTATT. Life was good. I was happy thinking i Knew all the answers to all life's big questions.
Now I am awake to TTATT, i am still happy. I am happy knowing i had the mental capacity to wake myself up from this weird cult. And i'm happy knowing the world isn't such a bad place and i can achieve whatever i put my mind and effort to.
The phrase "JWs are the happiest people on earth" is a bit pathetic really. People are either prone to happiness, or are prone to sadness. EACH INDIVIDUAL makes that choice themselves.
I have met an equal amount of miserable JWs and happy JWs. Both Positive and negative.
I have known a few people before becoming JWs (when they were studying) and they were pretty miserable. After they got baptized they were still miserable. Basically, they are prone to negative feelings, and a sad, negative outlook.
Same has worked the other way.
It is the same with any en-devour in life, not just religion. Employment, education, wife/husband.