Success isn't what makes you happy. It really isn't. Success is doing what makes you happy and doing good work and hopefully having a fruitful life. If I've felt like I've done good work, that makes me happy. The success part of it is all gravy.
Character gives us qualities, but it is in actions -- what we do -- that we are happy or the reverse. All human happiness and misery take the form of action.
Why, after all, should readers never be harrowed? Surely there is enough happiness in life without having to go to books for it.
What would there be in a story of happiness? Only what prepares it, only what destroys it can be told.