Have you ever heard someone exclaim, "I just want to be happy!" as if their life depended on it? I have, and probably even said it myself a few times in my past. But we should be honest with ourselves. Are we going to feel complete bliss every day of our lives? No. There is simply no way. It's just not rational.
Perhaps we would better off repositioning our goal: contentment. For some, its a novel concept, but I think it deserves some consideration. If your goal is to be content, you strive to take things in stride, assume the best, let go of the small stuff you can't control.