As it applies to self-awareness, congruency means that your thoughts and actions match each other. A lot of people live lives where they think one thing but behave in ways that aren't consistent with those thoughts. This creates tension and inner conflict.
One of the best ways to achieve congruency is to act in ways that are consistent with what you think. For example: If you say you're going to do something, do it; if you believe something, make sure your actions match. You'll feel happier and more balanced once you bring your thoughts and actions together.