Why???

Why, when you're having a perfectly good day, can one small little thing bring you down? From then on its like "whats the point for even starting out good when it's just gonna end bad?" Have you ever had a whole day where everything went good? I just want one day like that. But it always seems that there has to be one bad thing that happens to ruin it. Those days all I can say is why? Why me? Why now? Why here? Why this? Why God, why? That's all I want to know, why???