Sure, we grew up physically -- but emotionally, psychologically, and spiritually many of us are still stuck back there in early childhood. We never learned a "normal" way of thinking, feeling or reacting.
Over the years, those who have studied the "adult child" phenomenon have compiled a list of common characteristics which many people who grew up in dysfunctional homes seem to share. The following characteristics were developed in 1983 by Dr. Janet G. Woititz.
You may recognize some of them.
...guess at what normal is.
...have difficulty in following a project through from beginning to end.
...lie when it would be just as easy to tell the truth.
...overreact to changes over which they have no control.
...are extremely loyal, even in the face of evidence that loyalty is undeserved.
...tend to lock themselves into a course of action without giving serious consideration to alternative behaviors or possible consequences. This impulsivity leads to confusion, self loathing, and loss of control of their environment. As a result, they spend tremendous amounts of time cleaning up the mess.
You might want to read Dr. Jan's book Adult Children of Alcoholics for more detailed descriptions. You might take the Adult Children Screening Quiz to get an indication of how much you may have been affected by growing up in an alcoholic or otherwise dysfunctional home.