Constant fairness is an unrealistic expectation of parents because they have failed to factor in the most basic element of human error and their capacity to misjudge situation and overreact which is quite normal. While you can work towards the goal of being fair, do not be dismayed if you find yourself straying off the path. Parents are human after all. When parents think that they can always be fair, they have to realize that it's not like disciplining soldiers in the army. Each child is different and has his own temperament.
Some children are easy to talk to and reason with.
Others can be stubborn and naughty and will need a firmer hand. There is no way that one blanket approach can cover them all. Some children get shouted at more often because they don't respond to any other kind of discipline. Playing fair can backfire Parents should also keep in mind that by sticking rigidly to the 'always fair no matter what' attitude they may be doing their children a disservice. Children are entitled their special praise and privileges depending on their needs and when they earn it.