Life may be punctuated by "what ifs". But for those who survive a natural disaster, it is difficult not to feel overwhelmed by speculation about what might have been.

I was undoubtedly among the fortunate. Last Boxing Day, I witnessed the waves relentlessly creep forward until only the tops of palm trees were visible while on holiday on the south-west coast of Sri Lanka. For one fraught day, as the sea waxed and waned with wave after debris-strewn wave, we waited anxiously for news of four family members who were missing at sea on a fishing trip.

We were safely reunited after dark that night, but our fortune, however welcome, was quickly overshadowed by the extent of the devastation around us. One year on, the memories may be slightly less vivid but the impact of the tsunami has left its mark on the family in countless ways.

The transition from relaxed beach holiday to ravaging natural disaster was never going to have a predictable outcome. I spent days reporting on the apocalyptic devastation of the eastern coast, while my family, unable to return home early, helped distribute supplies to local hospitals.

When we arrived back in the UK, life on the surface appeared to return to normal - until, only days later, my mother suddenly announced that she was returning alone to Sri Lanka. She packed her bags and spent weeks working with a number of charities on an array of projects across southern Sri Lanka during the first few months of the year.

Having witnessed the extent of the devastation first hand, my mother's motivation was clear. "I felt very strongly that my contribution - however tiny - would be better than nothing. I was merely playing a very small role in a vast operation but there is still so much more to do."

Back on the ruined coastline, there was temporary housing to be built, toilets for refugees in the Buddhist temples of the hill country to be constructed, and traumatised children needing help with workshops where they drew their experiences.

But among all the heartbreaking stories we encountered, it was the experience of one family that moved my mother the most.

"I'll never forget," she said. "They had three daughters under the age of 10 who all died. The father was out fishing, and the mother thought it would be safe to take the children behind the train after the first wave came. But when the waves came back, they were swept away. The mother survived by clinging to a tree."

My mother's decision to return to Sri Lanka may have seemed impetuous, but the tsunami's lasting effect on her was to cast her priorities and her perspective far beyond our immediate family and its needs. Now, she is planning to return to Sri Lanka again in the new year.

Her determination to helphas also indirectly helped the family override the thoughts that continue to haunt us about how differently things could have turned out for us.

Every morning of the holiday before the tsunami, I had taken my two younger sisters surfing at around 9am - the time of the first wave. Only laziness had compelled me to give it a miss on Boxing Day morning. My boyfriend and I had been due to take the train along the coast to Unawatuna the following morning. Neither the train nor the hotel where we were due to stay survived.

For months afterwards few of us were immune from recurring water dreams, involving flooding seas in a variety of terrifying guises. And when my 14-year-old sister returned to school to learn that the mother of a fellow pupil had died in the tsunami, questions surrounding the arbitrary nature of survival inevitably bobbed to the surface.

But there have also been positive changes. My father spoke movingly at the time of the pressure of being responsible for the livelihood of the partners of three of his daughters, with whom he was stranded on the fishing boat during the height of the tsunami.

Since his return, he has embraced the notion of living life to the full, from buying a new home abroad to planning his dream sailing trip. The life of another sister has also changed dramatically. Five days after the tsunami, she became engaged to her boyfriend and is now married with a baby.

As candles were lit and prayers recited across South Asia yesterday to mark the one-year anniversary, we all stopped to remember in own personal ways those who had perished. But while the television pictures of the memorial services and the tropical beaches closed the gap in our memories that has gradually widened over the past year, the hows, whys and what-ifs seem destined forever to go unanswered.