Answer

This has caused much debate and some useful ideas are found at:

http://www.cs.rice.edu/~ssiyer/minstrels/poems/544.html

Try:

I don't say that the crappiness of my needing to work is balanced out by my
lack of courage in failing to find a more noble and less soul-stultifying
way of keeping body and soul together, like, say, coming up with the idea
for Post-it notes, or the personal computer. Or, say, making a living from
writing poetry. I'm not at peace with this set-up. But there it is --
work's a toad, and I'm a coward, and since work won't get better and I'm too
chicken to go it alone, I'm stuck.

Or

I think the last two lines are talking more about how if you had only
had the bad work and not the fear about quitting, you could change your
situation and have the freedom to do what you want. Or if you had the
good luck of already having that freedom but still have lack courage, it
wouldn't matter because you would never have to change you job. However
the man in the poem has both. He has job he hates and not enough courage
to quit and his desire to quit is out weighed by the strength he has to
do something about it.