What if there is no cause? What if I get depressed because I've been happy too long? A feeling could be just a stage in a long trail, or a crest in an infinite wave, obliged to sink again, and rise again. Sometimes all of us try to understand what makes us feel sad, and we try to fix it. Some wiser among us try to make themselves happy as often as they can. But sometimes no matter what you do you still sink. The higher you've managed to hold your crest, the farther you're going to fall. You can't support a wave.
And some would throw at me determinism. As if we had no control over our lives, but it seems to me that that is the beautiful thing of life is that there are things within us we can't control. Determinism is when your entire route has been laid out for you, like a painstaking multiplication of sines that you ride with no scalars in your hands. But you can affect how you will feel; it's just that you can't cause it. Life is far from determined. But you know that once you've risen long enough, or sunk low, you will even out.
I do have some effect on future events, especially when I am going to cause those events, like saving up enough money to buy a bike. But whether that bike will make me feel happy... it depends. So you see, it's neither determined nor controlled, and hopefully we can approach a Buddhist-style tranquility by accepting that we cannot remain "high" forever, and certainly not low.
Show of hands: how many other Westerners out there idealize Buddhism? <insert counter script here>