Answer:
Experience
Step-by-step explanation:
Based on this quote, Thoreau believes that truly wealthy people are those who are able to truly experience life. This is as much a physical quality as a mental one. Wealthy people are those who are able and healthy enough to work, to travel, to love, to meet others, etc. They are also the people who are not held back from experiences by things such as fear and regret. Thoreau, therefore, establishes that wealth is experience, and that it has nothing to do with money.