If you see a pair of shoes, a gadget or whatever your favourite “impulse buy” is, can you just ignore it? If you can, well done!
How about if it is on sale? Can you convince yourself that it makes no difference, or do you think – “it’s on sale, I want it, I’ll buy it some time so I might as well get it now”?
How did you get on? Not easy is it? This is the effect of it being difficult to “defer gratification”, we want what we want now, not in the future.
Most of the textbooks talk about the ability to “defer gratification” as something that children have to learn, assuming that adults can all do it. This is partly because the effect was first demonstrated in children and mainly because the psychologists and everybody else who has studied the effect don’t want to face the fact that they (and all adults) are subject to it as well
There is a classic type of experiment where children are offered a sweet and told that they can eat it now, but if they wait to eat the sweet they will get a second sweet (or a bag of sweets, or a better sweet, depending on the particular experiment) in ten minutes or so when the experimenter comes back. In theory, around a particular age children learn to “defer gratification”, to take less reward (or none) now, in order to have a bigger reward later.