To have characters with realistic psyches, you have to understand their childhood, and you have to understand how their childhood shaped who they are.
Look at your own life, your own fears, insecurities, deep needs. Put them down on paper. What is hollow in you was formed when you were growing up. Things you still need to prove, to find, to keep, were absent then.
Recognize needs, hollow places in the people in your life. See how their parents, their childhood events, created that personality.
Here is a list of parental types and possible resulting characteristics.
- Good parents, parents who indulged: expects the best, confident, often disconnected to other people’s grief, overwhelmed and dramatic about their own suffering.
- Violent, absent parents: very little discipline, will often run to immediate joys, pleasures, afraid of doing something wrong, insecure, self-blaming, irresponsible
- Unreliable parents: overly protective, overly controlling, often arrogant to assure their inner child that they’re worth something (they will feel that they are not worth parent’s attention)
Find the child in all of your adult characters. Who are they? How old are they? How often do they appear? How much do they drive your protagonist? Your characters will deepen if you understand their past.