Great - I can't keep my car plates up to date now...

Moral licensing. Just when I thought I knew how I thought, I think I don't know.

What happens when you remember a good deed, or think of yourself as a stand-up citizen? You might think that your shining self-image would reinforce the value of selflessness and make you more likely to behave morally in the future. But a new study disagrees.
Through three psychological experiments, Sonya Sachdeva from Northwestern University found that people who are primed to think well of themselves behave less altruistically than those whose moral identity is threatened. They donate less to charity and they become less likely to make decisions for the good of the environment.

Sachdeva suggests that the choice to behave morally is a balancing act between the desire to do good and the costs of doing so - be they time, effort or (in the case of giving to charities) actual financial costs. The point at which these balance is set by our own sense of self-worth. Tip the scales by threatening our saintly personas and we become more likely to behave selflessly to cleanse our tarnished perception. Do the opposite, and our bolstered moral identity slackens our commitment, giving us a license to act immorally. Having established our persona as a do-gooder, we feel less impetus to bear the costs of future moral actions. [More of a post well worth reading]

It could be we will be reaping the whirlwind of a generation of self-esteem boosting. But the researcher ends with a more optimistic suggestion:

Sachdeva is also interested in the types of situations where people seem to break free of this self-regulating loop of morality, and where good behaviour clearly begets more good behaviour. For example, many social or political activists drop out of their causes after some cursory participation, but others seem to draw even greater fervour. Why?
Sachdeva has two explanations. The first deals with habits - many selfless actions become more routine with time (recycling, for one). As this happens, the effort involved lessens, the "costs" seem smaller, and the potential for moral licensing fades. The second explanation relates to the standards that people set for themselves. Those who satisfy their moral goals award themselves with a license to disengage more easily, but those who hold themselves to loftier standards are more likely to stay the course. 

We can overcome the constraints of our physiology with discipline and good intent, I believe. But is also helpful to understand why others act as they do.