Reach
What is the point in pining for things out of your reach? With so much energy available, yearning is a waste. But the mind (or the heart) struggles with the current sadness and so it escapes towards the imaginary, where it can't really picture the wholeness of the situation.
We can't see reality as a whole. There are always aspects of it that elude us. So, instead of spending resources daydreaming, one should focus on the situation at hand, and try to find ways to make it better.
Yet, building the now without a vision towards tomorrow might be a dangerous prospect.