Being in a life/death situation with someone always brings you closer.
People can say a lot without every opening their mouths through the form of non verbal communication.
In the case of relationships, understanding non verbal communication can help someone know what his or her partner is really thinking.
For example, if a woman tells her boyfriend she is happy going to a football game instead of shopping, but she is standing with her arms folded facing away from him, her body language clearly says she is not happy with the decision.
Non verbal communication can also be helpful in certain professions such as law enforcement.