Your job as a parent is not to make your child happy. Your job is to make your job obsolete one day. Your job is to raise independent, capable children.
Will they be perfect when they reach the age of 21? No. But they will be ready to make their own decisions, learn from their mistakes, and grow into functioning adults.
They will do this not because you have made sure they are happy, and have had wonderful childhood birthday parties and experiences. They will do this not because you have shielded them from all consequences of their actions. They will do this not because you have protected them from all unpleasantness in the world. They will do this because they will learn that they are stronger than they thought they were. They have come through difficulties kicking and screaming but they have come through. They learned some valuable skills along the way, like the skill of being able to force themselves to do something they don’t like doing.
Will they be happy during these trials and difficulties? No. But they will be lucky to have a parent who believes in their ability to grow and learn and to become independent adults. They will be lucky to have a parent who was strong enough to allow their children to be unhappy long enough to grow. And they will take these very valuable lessons and skills with them into the rest of their lives. They will be much better prepared for college, for their jobs, for marriage, for parenthood, and whatever else life decides to throw their way. None of us can choose happiness for ourselves or our loved ones. We can, however, love our children enough to teach them to make friends with discipline. Happiness may then visit of its own accord.