Hi Trang, thank you for the tough question! I consider this a burning question for myself also :)

What I do know is that being "balanced" is not a destination but an ongoing journey. Albert Einstein once said “Life is like riding a bicycle. To keep your balance you must keep moving” and I would like to be bold enough to add "To keep your balance must keep moving FORWARD".

I believe we can tell we are balanced when we are moving forward (making progress) towards our vision for our ..
1. Life: Having peace & satisfaction in who we are becoming
2. Family & Relationships: Having peace & satisfaction in our relationships
3. Work: Having peace & satisfaction in what we do & knowing it makes a difference to others

So here are some suggested questions to measure our balance:
1. Do I love & respect the person I see in the mirror? Am I happy with who this person is becoming? If there was something I would change today, what would it be?
2. Am I at peace with all my relationships? Despite the differences & conflict, have I forgiven those who have wronged me? Even if those people never change, can I still continue to treat them with love & respect?
3. Do I have a real passion for what I'm doing? Or is it just a passing interest? Am I serious to go the long term with this? If I did not have to worry about time and money, what would I do to make the lives of others better?

If we can answer yes to most of these questions, I would say we're moving in the right direction and keeping that balance we seek :)