You can rationalize or irrationalize unhappiness all you want. It doesn't make a difference as we are human and circumstances and events are going to make us unhappy. Its like convincing yourself that monsters don't exist when your alone in the woods at night. You may know there is no reason to be unhappy, but that doesn't make you happy.
Its what makes life worth living though. Our being human is the only thing that keeps sentience from destroying our minds. Sadness, happiness, anger, hunger and the like are all things we'll always experience and sometimes crave even when we know everything about them. Sadness will go away the day we are no longer human.