Children are often told things like, "if you can imagine it, you can become it," "when you wish upon a shooting star..."and "the sky is the limit." Almost always this dream is interrupted, often rudely. Most of us are lucky enough to keep perspective, and to therefore keep dreaming. Some things work out, others don't.
Being fundamentally optimistic, it is human nature to want what is meaningful for us. We are driven to constantly redefine and explore what is of highest value and significance. In many ways this entire dreaming process, the discovery and rediscovery of our heart's passions, is the greatest reward.
Weather you're growing up, or retiring, getting married or starting a company, having a baby or burying a loved one, day dreaming is an incredible gateway.
There is another childhood phrase: "the reward for patience is patience." I would like to alter it slightly, "the reward for dreaming is dreaming."