It was a morbid week. It began with a visit to a friend who was dying of AIDS. It had reached a point where he couldn't speak anymore. I tried to get him to grip my hand in response, but it was limp. He looked glassy-eyed at me; I couldn't even be sure he recognised me at all. He was 48 going 49.

Before the week was over, I got news that another friend had passed on. He was among the sweetest people I ever knew. He had no airs but a self-deprecating humour, often referring to himself as "this ditzy girl."

Now he's gone, though I had kind of expected it ever since he was diagnosed with lymphoma about 18 months earlier. Chemotherapy and bone marrow transplants were tried, but to no avail. His last x-ray showed a body "full of stars" as another friend described it, indicating widespread metastases of the cancer. He slipped away quietly one morning. He was only 36.

Some of us will die much younger than we expect. We may not have as much time as we think. And inevitably the question arises, what have we done? What have our lives amounted to?

Despite how it looks, this is not a question to be asked when we come face to face with the end. In the moment of despair when we hear the diagnosis, it is not likely to be anywhere on our list of pressing concerns. So the only time that that question may be worth asking would be when we are well and actually have a choice about what we want to do. In other words, now.

Heterosexual people with children would very likely point to them and say, I have given them the best part of my life. I have provided for them, raised them, imbued them with values and sent them on their way. And these would be great achievements, often representing 20 to 25 years of sacrifice.

For many gay people, no such obvious answer lies at hand. Our lives do not fit into any pre-planned program, freeing us to choose other kinds of good work, but by the same token, freeing us too to not do anything meaningful at all.

We can live a life of shagging and partying, and as grow a little older, one cocooned with a partner, embellished with the occasional round of social gatherings. When we're gone, somebody can be trusted to say we were kind and generous, jovial and spirited. We made pretty little cupcakes or a wicked martini, and we were sincere with everyone we met and the stray cat too.

We were a hardworking employee, someone could be relied upon to say. Or perhaps a successful boss in our own right, raking in the dollars. And then what? Die like Nina Wang with billions to her name but unable to take a cent with her? What's the point?

Why should there be a point? How much difference can anyone of us make? In the end, the icebergs will melt, species will become extinct, nations rise and fall and millions more will still die of hunger and pestilence, war... and jaywalking.

Indeed, it is impossible to rationalise why we should even try to do "good work" (however we define it) in our lifetimes. There will always be the problem of scale. What little we can achieve will always be dwarfed by the enormity of processes churning on inexorably in the world. What difference does a shrimp make to an ocean's current?

And yet, because we are sentient beings, we at least know to ask the question: How have we used our time on earth? And for some of us, hopefully, it is not satisfactory merely to say, rationally speaking, there's a 99.99 percent chance whatever we do will be futile, and that nothing much will change, so why bother.

It is not supposed to be rational. Nor measurable, nor something we have to justify to others. It really is a matter between ourselves and our God or conscience - how we have used the gift of life.

A friend of mine, on reaching 40, said he was going to wrap up what he had been doing as work. He was going to quit business and go off to Indochina to set up an orphanage. He told me his father had been a good but quiet man: papa had kept a low profile and provided for his family. But now, years after his passing, few even remember him. His imprint on this world was so light, hardly any lives except his own family's had been touched by him. My friend wanted to do more, even though he was gay with no children of his own. "I must have an impact on more lives than my father ever did," he told me. "I want to leave something of value behind."

Just today, I read on Yahoo about a man who hangs around a Greyhound bus terminal in Alabama. Generally long-distance buses like Greyhound serve the poor and underprivileged; the middle-class and better off prefer to fly. This man befriends people at the terminal - the old, the unemployed, the newly released from prison - offering them words of comfort and encouragement while they wait for their bus. For a few moments, they get a friend and a listening ear.

Closer to home in Singapore, we have Jerry Siah and his gang, who visit old folks' homes regularly, giving these places a new lick of paint and cheering up the residents. We have the volunteers of Oogachaga who spend hours manning hotlines, just being there when someone somewhere needs a friend to talk to.

We also have filmmakers who struggle against the odds to make films that let the marginalised speak and teachers who at some personal risk, find ways and means to open pupils' minds to a world larger than the state curriculum allows.

They set good examples. Whether we have 36 or 48 years, or for that matter, 95, it would be nice to be able to say it's been a life lived. Not just for ourselves, but for others as well. And that we will leave tracks on the ground.

Alex Au has been a gay activist for over 10 years and is the co-founder of gay advocacy group People Like Us. Alex is also the author of the well-known Yawning Bread web site.