Both selfishness and generosity distort how we see our impact, but the selfish view is more contagious

People can sometimes make decisions that benefit them but are less advantageous for someone else. In these scenarios, they might convince themselves that their choice causes little harm to others or that an alternative would not make much of a difference. The same can happen in reverse, as people who act generously may overstate how much good the outcomes of their choices did for others.