An experiment was run by Walter Mischel with four-year-olds back in the 1960s. Each child was brought into a room in which there was an Oreo cookie. The child was told that s/he could have the Oreo right then and there—or if s/he waited 15 minutes, could have two Oreos instead.
Some children opted for single Oreos immediately, while others said they would wait for two. To actually get the two cookies, the subject had to sit in the room with nothing else besides a plate with the one Oreo on it—and not eat it for the 15 minutes.
Some succeeded, others did not.
Now, here's the interesting part. The experimenters then checked in on these kids years and even decades later. Those who had the discipline to wait for the second Oreo cookie scored higher on IQ tests and were more successful in life.
Were you the type of kid who would eat just one cookie or wait for two?