Q: Gurudev, what is the significance of the wedding ceremony? If two people love and respect each other, can they just make a decision to live together?

Sri Sri Ravi Shankar: Marriage ceremony is a commitment. You live together with a commitment. When there is a commitment, you have full trust in each other. One aspect of your life is set. That is what is marriage.
Otherwise, the mind keeps looking for a partner. In marriage, that looking for a partner thing comes to an end, 'Okay, I have found a partner, I am set.' So now you can focus on other things.
When there is commitment, it puts you on track.

http://www.artofliving.org/in-en/what-sri-sri-said-today