Why try when we all die anyway?

Last night a fellow used the argument that effort in a certain direction, in this case recovery from addiction, was futile because of Keynes' assertion that, in the end, we are all dead. I cannot help but believe that this is fallacious reasoning because, although the assertion is perfectly true, there are certainly valid reasons for putting forth effort towards these sorts of goals despite it, such as, for instance, extending one's own life.

Is this a fallacy, formal or informal, and, if so, what is it called?

This is a philosophical concept known as fatalism . Philosophies such as these exist because we are not purely logical creatures. Virtually everything we do is reduced to some kind of emotional component. Because of this, virtually all of us have no problem with using a metric such as "well-being" as the foundation of our actions, behaviors, and decisions. The problem is, there are many people who lack what might be considered a normal range of emotion, and attempt to use reason to get to some fundamental "why," which can't be done. Reasons ultimately reduce to an affective (feeling-based) foundation, not a rational one. So if we ignore affect (feelings), fatalism is the outcome.

In summary, I wouldn't call this a fault in reasoning; rather, it is an over reliance in reasoning . This might be better understood as a biological defect in the brain.

If.the goal in evolution is to continue the species then there is inherently a fundamental drive to survive in all organisms as a basic requirement of having offspring is being alive (the ones which didn't have this died out).

The human brain has parts which developed more recently which are to do with thinking, rationalising, talking, creativity, etc. but there are older parts which are more instinctive and which take over in times of danger; during the freeze, flight or fight response there's not a lot of rational thinking going on.

So for the most part I'd say that the question is just irrelevant with regards logic, and perhaps only relevant in the sense that people who develop thought processes which lead to just giving up, because they don't see the point, are taken out of the gene pool by natural selection.