Futility and the Notion of Gain
Life may appear futile simply because we think it is meant to provide gain.
Gaining ideas, as the name implies, refers to ideas that have some form of reward associated with them. Another way to express this is that gaining ideas operate under the notion of purpose. We cook breakfast because we are hungry, go to work to earn money, fix the roof so we don't get wet, and so on. In everyday life, gaining ideas are fine and dandy, provided we don't overdo it. Outlandish ambitions are unlikely to be realized, and so gaining ideas can be a source of considerable disappointment. Your first video showing your singing abilities is unlikely to rocket you to fame and stardom, and disappointment will be the only result. Modest gaining ideas are the engine of life, and without them, nothing would happen.
Things start to get complicated when we consider issues deeper than cooking breakfast. As Spinoza points out in his Ethics, the universe itself is not driven by gaining ideas or purpose.
Now all the prejudices which I intend to mention here turn on this one point, the widespread belief among men that all things in Nature are like themselves in acting with an end in view.