In my opinion we can learn more from children than the best guru or enlightened master can teach us. Children, when they are young, naturally live in the now, in the moment. This is a great teaching. It will keep you young and alert. If you stop for a moment and are willing to be open, a piece of that natural playfulness and awareness will be transmitted to you; changing you forever. Changing your priorities and teaching you what is really important and what is not.
If you have not heard of Eckhart Tolle before and would meet him for the first time, your first impression would probably be that of a very ordinary, simple man. You may even find him a bit boring when you hear him speak. But don't judge a book by it's cover as this man is one of the most remarkable (spiritual) teachers of today.
Byron Katie was severely depressed and had been suffering for many years. Then one morning she woke up and noticed a shift in her awareness. She found out that her thoughts are not who she truly was. She also discovered that by asking four simple questions she could investigate her thoughts and find out if they are true or false.