Comment on a Henry David Thoreau quote

"Children, who play life, discern its true law and relations more closely than men, who fail to live it worthily, but who think they are worthier by experience, that is, by failure."

When do we become adults? Children see life at its best. They are eager to explore, they want to suck the spirit of live. Children are free from the economic endless pursuit, and free to be inspired by nature. On the other hand, adults only see what they've been taught to see; they miss many parts they could see as kids because they only care about the world that society and traditions have created in their minds, losing the true spirit of things. In order to become part of that world they have on their minds many mistakes are made. Such failures, we keep calling experience, are nothing more than a continuous chain of bad things we've made that makes us assume we are growing up. The sad part is that we can only see it in hindsight when we have become "experienced".

Not bad. At least, as far as I can tell, not knowing the assignment instructions. Mostly, I'd say you should add in more concrete, specific examples to demonstrate the abstract ideas you are discussing.

"When do we become adults? " Nothing in your commentary directly answers this question, which makes it an odd introductory sentence.

"On the other hand, adults only see what they've been taught to see; they miss many parts they could see as kids because they only care about the world that society and traditions have created in their minds," I would add a concrete example or two here to demonstrate the truth of this statement.

"In order to become part of that world they have on their minds many mistakes are made. " I'm not entirely sure what you are trying to say in this sentence. Revise

"Such failures, we keep calling experience, are nothing more than a continuous chain of bad things we've made that makes us assume we are growing up." Again, adding in a concrete example or two might clarify this a lot.

I'm sorry the assignment instructions is :

Copy a sentence or refer to a thought from the assigned essay : "Where I Lived, and What I Lived For". Then write a statement, a topic sentence that expresses your idea or response. Next, write a paragraph of 100 words that supports your idea.

It is true, could you help me with an introductory sentence??

I wish to add examples but then my paragraph will be to long.

Ah. Yes, you don't have much room for anything else given those instructions, which is why posting the instructions along with your draft is always a good idea. As for an introductory sentence, the instructions ask you to write a summary of your main point, and to use that as your first sentence. So, all you need to do is summarize the main point you want to convey through your paragraph, and that will give you what you need for your introduction.

How about this?

Does adulthood takes away the true spirit of life? Children see life at its best, eager to explore; they want to suck the spirit of live. Children are free from the economic endless pursuit, and free to be inspired by nature. On the other hand, adults miss many parts they could see as kids because they only care about the world that society and traditions have created in their minds, losing the true spirit of things. They become immerse in work, and getting financial status, and bury themselves in everyday problems. Many mistakes are made along the way to adulthood, mostly in our day-to-day relationships with our loved ones. Such mistakes, we keep calling experience, are what makes us assume we are growing up. The sad part is that we can only see it in hindsight when we have become "experienced".

I like this but am confused by the last sentence. What is the "it" that we can only see in hindsight? (In general, when using a pronoun such as "it," the noun or noun phrase for which the pronoun stands ought to be in a preceding sentence.)

the "it" stands for the fact that we have lost the true spirit of life.

maybe It is better this way:

Such mistakes, we keep calling experience, are what makes us assume we are growing up. The sad part is that we can only realize we've lost "the spirit of life" in hindsight, when we have become "experienced".

Yes, that is much stronger! In general, we tend to say "it" when we are being vague. Taking the time to specify what "it" is often leads to much more effective prose.