Sometimes when you walk down memory lane, you get hit by a truck. And you don't see it coming. It doesn't kill you. It just lays you flat, keeps moving over you or, if you're unlucky, reverses back and does it again. These uninvited vehicles are the shadowy traffic in your life. They are the memories that you would prefer never to see again.
Fortunately, there are scientific breakthroughs regularly announced for all manner of murmurs and ailments that hold out hope for the sufferers. The timeline for these things is never precise, as it can't be, but it is a sliver of light.
And one shone through yesterday with the news that neuroscientists have found the gene that has oversight of archiving memories, and thus the responses that can occur when that memory comes to the surface. It is called Tet1.
The research originates from the Massachusetts Institute of Technology and, of course, it involves that furry little helper of humankind: the mouse. Scientists delving into an area of the brain called memory extinction used two sets of mice, which were given a shock every time they entered a cage. But one bunch had its Tet1 gene ''knocked out''. When they were put back into the cage, but not given the shock, the ones without the gene were still in fear.
Li-Huei Tsai, director of MIT's Picower Institute for Learning and Memory, says: ''What happens during memory extinction is not erasure of the original memory. The old trace of memory is telling the mice that this place is dangerous. But the new memory informs the mice that this place is actually safe. There are two choices of memory that are competing with each other.''
The Tet1 and its associates were busily overwriting the bad memory. So, if the activity of Tet1 could be stimulated, perhaps the nasty stuff could be erased? As the researchers pointed out, this could help those who suffer post-traumatic stress disorder. Or it could help oneself deal with the spectres that dwell in the dark chambers of one's past or one's country's past.
The film Eternal Sunshine of the Spotless Mind touched on this a few years ago when Jim Carrey and Kate Winslet underwent memory erasure of each other. It was a romantic comedy.
This type of scientific disclosure allows for all sorts of flights of fancy. Imagine, one could erase memories of the government of John Howard, or to be politically fair you could also erase the era of internecine fighting in Labor. Actually, you could erase the entire pitiable, depressing past decade or so in politics.
No more would a perfectly contented day be split asunder by the image of warrior Howard looming over the shoulder either declaring ''We will decide who comes to this country and the circumstances in which they come'' or that invading Iraq was in our national interest.
Nor would it be shredded by the volley of knives and arrows being propelled towards Kevin Rudd, then Julia Gillard, then back to Rudd by their own colleagues. George W. Bush, Dick Cheney, Donald Rumsfeld, all could be gone. Saddam Hussein gone. Osama bin Laden gone. Their memories replaced with a rainbow.
This Sunday, one huge army of fans could erase the memory of a grand final loss. Supporters of the Swans and the Storm, both premiers last year, could have already had the treatment after last weekend's efforts, and continuously bask in past triumphs.
Followers of the Australian cricket team could receive regular treatment, both for the past few years and in advance for the upcoming Ashes series.
At a personal level, the bitter memory of a cruel word or act upon yourself could be overwritten. This could, however, lead to a plunge in work for therapists. Perhaps the inverse might come into effect. Dear therapist, I'm worried I don't seem to have any bad memories at all! My life can't be perfect, can it?
One of humankind's most powerful forms of behaviour would also be neutered: revenge. For what could be avenged if there was no calumny eating away at a soul? Also we would never have had such immortal words as ''Ah, Kirk, my old friend. Do you know of the old Klingon proverb that revenge is a dish best served cold?'' The TV series Revenge also would not exist. Alas.
Of course, there is the other side of the coin, minted on the premise that what doesn't kill you makes you stronger. Painful memories can be the driver for a person to try to get as far away as possible, physically and mentally, from the scene of the trauma. However, it's not necessarily true that time, and distance, heals all wounds - not if the memory still lives.
Our lives are our memories and vice versa, but if you could avoid forever the bad moments, would you? Eternal sunshine can be phrased another way: forever drought.
Warwick McFadyen is a senior writer at The Age.