very good thought, I think we should learn from history it has many lessons for us and try not to repeat mistakes we or others did in past. But I feel sad when I see individuals or even nations dont learn from history, that might be annoying for some of US freinds but USA invaded Iraq even after thay had some hard lessons in vietnam. 

People do learn from history. That's why we don't kill the every other person we don't like and we are more civilized than before.

Do we never repeat the mistakes we made before? Well, no. Its not possible. Some things need to be experienced, they can't be learned.

I think people never learn from their ancestors'mistakes. At best, they will admit them but find excuses.

I also believe that history makes for a very difficult reading. Everything is sanitized and distorted. We must rely on additional primary sources, which are also sanitized and distorted. Also, we apply our own principles to what we read, which makes it even more difficult to see the true facts.

The big advantage of hisatory is that people can make their life more ideal.

Your comments are very wise and I think everyone would agree with you.

Here are a couple of suggestions about what you wrote:

History are lessons for the present and guidance for the future.[space after all punctuation marks]sometimes people can avoid making same mistakes that our ancestors made before. what's your opinion?

History [this word is singular, therefore the verb must be "is", but "is" is not the right verb to use]

History provides/provides us with/teaches us/shows us lessons for the present and guidance for the future. [space after all punctuation marks]

Sometimes people can avoid making the same mistakes that our ancestors made before.

[ancestors came before us, therefore the mistakes they made also happened in the past. So, it is not necessary to say "before" because it is redundent, i.e., the mistakes were made in the past]

What's your opinion?

Your comments made me think of a famous quote from Winston Churchill, made around 1945:

"Those who fail to learn from history are doomed to repeat it."

And your comments say the same thing... well done Arlene.