Dr. Wendy Walsh: It will be dark and cold. There will be crowded airports, sweating throngs, pat-downs and whining toddlers. There will be bad airplane food and lack of sleep. But at the end of the journey, my kids and I will be met with pairs of eyes that squint in shared formation. People who carry our genes. Family.

Holidays bring a specific form of stress. Getting together with relatives is the closest thing we have to a time machine. At holiday tables, we are strapped in our seats by the centrifugal force of old family systems -- a world we'd ventured away from years ago, never thinking about a return ticket. Slammed back in time, the favored child still gets a wink from Mom, though his graying hair and paunch suggest a lost luster. The sister-to-sister sibling rivalry finds a modern battle as polite mothers now shoot competing stories of their children's accomplishments.

The clash of social class is epic. Decades of movement up or down networks of human ladders erupt over brands of mustard, types of lettuce or beverages. Dijon, arugula and Cabernet strike condescending blows at cousins who wash down iceberg and American yellow mustard with a frosty malt. The end of unemployment insurance seems a more patriotic conversation than environmental dangers, as one camp focuses on practicality and another on ideals, all designed to advertise social class. The family holiday rendezvous is a bid to flaunt the colors of our new world and a desperate attempt to avoid slipping into a familiar trance of the old planet. But it rarely works.

The powers of family psychological systems are like kryptonite, disabling our most sophisticated mental strategies. But we still go. We make the pilgrimage. At least, most of us do. Others avoid. The characters played by Vince Vaughn and Reese Witherspoon in the film "Four Christmases" plan a yearly tropical vacation continents away from their families. Other folks drown in work. Still others dip in for a quick drink or meal and then jet off, unscathed by anything more than small talk.

Many who avoid family attempt to play catch-up years later at deathbeds and beside tombstones. But not us. We are the brave ones who climb into the time machine. And we do it for good reason. We do it because most of our families render us powerless to pretend, yet empower us with something else. The safety of a biological connection. We share genes, we share childhoods, we share pheromones, we share humor, we share love. This shared sense of belonging is the reason that we will bust our bank accounts to fly to the wedding of our crazy brother who is marrying a girl on a mountain in Mongolia. It's why we open our homes to cousins. It's why we spend hours cooking for people we haven't talked to face-to-face in a year. Because they are us.

When we are in their company, we are reminded of our familiar beginnings. There is some feeling of security in that. And if there were many old blows and injuries, we can also use this time to make right. To process more. Or simply to grieve the losses. Seeing a formerly abusive father, now old and weakened by alcohol, we can tend to the child in us whose childhood losses were so tragic. And we can look through the eyes of an adult at our tragic perpetrator and maybe even have compassion for his flaws.

We are all flawed people. And we live in an imperfect world. But in the presence of our family, we can have a feeling of belonging. Through the strengths of our family, we are reminded of the good in us. And through their flaws, we are given unique opportunities to mourn and forgive.