This quote essentially speaks to the vastness of possibilities that surround us. The "space about us" refers to the opportunities and potential that exist in our lives. We often limit ourselves by thinking small or confining our ambitions to what is immediately visible or achievable. Thoreau suggests that our horizon, or the limit of our experiences and knowledge, is never quite at our elbows, meaning that it’s not within our immediate reach or grasp. There’s always something more to explore, learn, or achieve.

The horizon is a metaphor for our future or our goals. It’s a moving boundary; the closer we get, the further it seems to retreat. This is not to discourage us, but to remind us that growth and learning are continuous processes. There’s always room for expansion, for pushing our boundaries, for stepping out of our comfort zones.

In today’s fast-paced, goal-oriented world, this quote is a reminder to not get too caught up in the immediate, the tangible, or the easily achievable. It encourages us to dream big, to aim high, and to constantly strive for growth and improvement. It’s a call to not settle for what is within easy reach, but to stretch ourselves, to challenge our perceived limits, and to continuously expand our horizons.

In terms of personal development, this quote can be a guiding principle. It tells us to never stop learning, growing, and evolving. It encourages us to not limit ourselves to what we already know or can do, but to constantly seek out new knowledge, skills, experiences, and challenges. It’s a reminder that there’s always more to explore and discover about ourselves, others, and the world around us. It’s an invitation to embrace the journey of personal growth and development, to continually push our boundaries and expand our horizons.