All I ask of you, especially young people … is one thing. Please don’t be cynical,” O’Brien said. “I hate cynicism — it’s my least favorite quality and it doesn’t lead anywhere. Nobody in life gets exactly what they thought they were going to get. But if you work really hard and you’re kind, amazing things will happen. I’m telling you, amazing things will happen.
When you are idealistic about how others will treat you in your relationships, you become more attractive as a relation partner. This helps you attract better partners. Later in life, when you are attached to particular others via relations, you are better off being suspicious and cynical, as this gives you a negotiation edge when threatening to leave your partners, and discourages them from exploiting you.
If cynicism correctly applied involves closing potentially negative doors and idealism correctly applied helps to open potentially positive doors, then someone young still searching for their niche should not be quick to engage in the former over the latter. Of course, there are actually more direct signaling reasons to act age appropriately. A cynical point of view is often an attempt to signal knowledge and experience, and may people would find this signal to be in-congruent coming from a young person. The cost of sending this signal is the doors that it closes and the benefits that accrue to a young cynic are generally small if people don't believe the young cynic is capable of adding value. So the real lesson is that young people should be wary of spending resources signaling something that isn't going to work.