Self-knowledge reflects each person's definition of who he or she is -- or at least thinks he or she is. It includes physical features, such as height and eye color, as well as more intangible characteristics, such as a person's strengths or beliefs. Given that no one knows more about you than you do, it's surprising just how typical it is for a person to demonstrate a lack of mastery over his or her sense of self. Psychological studies repeatedly find that people are terrible predictors of what will make them happy, and even worse at knowing what exactly they are feeling at any given time [source: Vazire].

Why is it so hard to master self-knowledge? Part of the problem could be our oh-so-fragile egos, which many of us will do anything to protect. The subconscious and conscious minds constantly work together to come up with excuses and rationales for our bad habits, behaviors and negative emotions. Psychologists call this a self-protective bias, in which we somehow manage to shift all failures away from ourselves. This bias may protect our egos, but it also keeps us from seeing ourselves as we truly are. One of the best ways to keep your mind from playing these sorts of tricks on you is to ask someone you trust what he or she thinks are your strengths and weaknesses. If you're not ready to open yourself up this much, try seeing yourself through someone else's eyes.

Social influences and the media represent another obstacle in the path to self-discovery. We often try to imitate the people around us in our attempts to thrive in social situations. Many people have a work self, a friend self, a family self and any number of additional masks to help them fit in or succeed in different situations. If you're constantly changing, or modeling yourself after other people, it can be tough to pin down exactly who you are.

Perhaps the most important reason that self-knowledge is so hard to master is that we're afraid of what we might find. Real self-examination requires facing uncomfortable truths, and taking the good with the bad. Discovering these negatives about yourself can often spur you to change, but the process isn't easy. If you truly want to expand your sense of self-knowledge, tackle fear by thinking about all the things you have to gain. Self-discovery can help you fix bad habits, celebrate your strengths and become the person you truly want to be.

Everyone has an image they'd like to present to the world, but many people aren't good judges of how well that image fits them. We tend to see ourselves in the best possible light; we'd like to be thought of as capable, smart and good-looking. To admit that we're not any of those things would be a major blow, so we tend to avoid even considering where we stand with regard to these traits.