Humans have a tendency to think in a black-and-white manner, leading us to fall into the trap of the Nirvana fallacy. This is when one compares the real world to some perfect yet unrealistic alternative, causing reality to pale in comparison. Thus, it causes us to believe that many things are not worth doing as they are insignificant compared to this alternative.
For instance, the notion of the drop in the ocean means that we tend not to do altruistic things as we believe that it will not make much of a difference in fixing poverty or cure the world of cancer. Not only does the fallacy apply to how we see the world, but it affects day-to-day life too. People are so afraid of not being able to achieve an ideal, perfect future so ironically they do nothing. This is a major reason procrastination happens, as the person believes that if they do something now, it will be inefficient. They then plan for a perfect opportunity to start doing work, and a vicious cycle begins. Thanks to this way of thinking, people often miss out on a great job opportunity or a lovely girl or a chance to change their life just because it was not perfect and did not live up to their expectations.
In fact, people often fail to see the small steps and only see the big picture. So if someone tries to make an improvement (e.g. going on a diet), others will ridicule that person by saying that going to the gym every week is not going to turn you into an Adonis, ergo it is pointless.
The Nirvana fallacy is also useful in debates. One can create a false dichotomy (that is, a black-and-white argument) and compare someone’s argument to an unrealistic argument. When someone makes a suggestion, you can attack it by pointing out one flaw and show how it is clearly not a perfect solution (even better if you provide an example of the argument failing). This will automatically disintegrate their argument. For example, if someone proposes a new idea, you may point out how someone may abuse the new system or provide a case when a similar idea failed. However, be warned that this method can easily be rebutted with common sense, so one must use it in a convincing way and distract the audience from the fact that it is absolutely ridiculous.
(The Garden of Earthly Delights by Hieronymus Bosch, click for larger image)