The job of parents, in my opinion, is not to make a child happy. The key to parenting is to teach children how to create happiness in spite of problems and challenges. This can be done through personal example, as well as emotionally and intellectually supporting the children when they face problems.
Too many parents try to protect their children from problems and frustration. On the other hand, problems and frustration are motivating. They push children into developing their resources. You can only help children to find long-term happiness if you do not insist that they should be happy all of the time.
As with all life advice, use your common sense when making decisions. Don’t exaggerate. Find balance. Listen to your gut. And relax. Even if you were a perfect parent, it wouldn’t be good for your child.