It is the instantly recognizable thumbnail of a widespread social ethic. The phrase 'do your part' in its various conjugations is universally understood as a good thing. It is an appeal anyone can make with a reasonable expectation it will meet with affirmation. And it needs to stop.
Picture a large heavy object with a crowd of people standing around it at even intervals. Divide the weight of that object by the number of individuals and you have the amount of effort it will take each person to lift it. If everyone just 'does their part' a task is accomplished which one person alone or a few people would find difficult or even impossible. It sounds straightforward and fair right?
The problem is that in life people aren't positioned around that object at even intervals. A great many are piled up in certain areas and other spots have only a few people nearby. Furthermore, the object isn't a nice even density. It is heavier at some corners than others and the heavy spots don't always line up where the large groupings of people are. And the people aren't all equally strong. Some of the people can't expend as much effort as others. And it's really foggy and the people can't see each other and no one really knows how much effort another person is putting into lifting the weight. All we know is how much effort WE are putting in.
'Doing your part' is just another way of letting the weight stay on the ground. It is a moral escape clause. It allows you to feel good about yourself and even seek approval from others without having accomplished anything. The truth is that most difficult things in this world are going to be accomplished by a minority of people doing much more than their part. This is partly because life is unfair. Partly because some people are gifted in ways others are not, and partly because some people get off their ass and get to work while everyone else is doing their part.
An apocryphal statistic that floats about in churches is that 20% of the people do 80% of the work. Usually this is said as a lament. "If only we could get those other 80% to do their part, wouldn't it be wonderful!" Without a doubt life would be improved if everyone was equally motivated, talented, and provided equal opportunities to work on the projects that are important to me. But none of those projects are ever going to get completed if I wait for that miraculous day to arrive, or if I keep putting in mediocre effort expecting everyone else to meet me halfway.
Here is what Jesus has to say about doing your part: "Some workers arrived at dawn. Some later in the morning. Some in the afternoon. Some workers arrived just before the end of the day. All the workers got paid the same wage." Deal.