According to Wikipedia (which cites a slightly dubious source that I can't verify), Stevens felt the message of this song was "uplifting" and he has called it an "optimist's anthem".
This song was, of course, written before his conversions to Islam but as Morning Has Broken suggests he has been religious all his life. In the bible, St. Paul advocates that all Christians should keep "faith, hope and love. Indeed, Moonshadow contains other religious themes:
Did it take long to find me? I asked the faithful light.
The title Moonshadow can be taken literally:
"So there I was on the edge of the water on a beautiful night with the moon glowing, and suddenly I looked down and saw my shadow. I thought that was so cool, I'd never seen it before."
- Yusuf Islam interview with Chris Isaak, 2009
So the "faithful light" here is a wordplay both on the light of the Moon and the light of God, and how an appreciation of the former can lead to one of the latter. An optimistic interpretation thus seems fitting.
Although the melody and chorus are uplifting, the cited verses go against the grain and appear rather grim. Reading the whole verse it seems clear that this is a case of dramatic contrast. Stevens suggests a number of pretty dire occurrences:
And if I ever lose my hands, lose my plough, lose my land
But then finds a positive note in each:
I won’t have to work no more
In doing so, he highlights how important it is to remain hopeful and optimistic.
Worth noting that his choice of body parts is interesting in itself. His linking of "hands" with "plough" and "lands" is decidedly anachronistic in tone. "Eyes" are mentioned in the Bible repeatedly, especially as a figurative motif (i.e. "an eye for an eye", "speck in your brother's eye"). And in terms of the mouth, silence ("I won't have to talk no more") has long been seen as a religious virtue.
All of this would tend to support the interpretation that this is a song about hope, inspired by its importance in Christianity.