It's easy to get pessimistic when we consider where we think we should be versus where we are in terms of space exploration and exploitation. This document from 1977 should dispel some of that pessimism.
While we are not as developed as an optimistic scenario would have had us, we have outperformed pessimistic scenarios. We are roughly in line with or marginally ahead or behind the moderate scenario forecast by big, NASA brains before I was born.
So its R okay to be frustrated. We are certainly missing some opportunities. Still we keep moving forward, and Humanity's skyward expansion continues.
Here's the 1977 document:
http://www.dtic.mil/dtic/tr/fulltext/u2/b310563.pdf