I don't have time to write this but I want to talk about instant gratification. It's a reason I'm a behaviorist even though behaviorism is so often terribly applied.
I tend to try things one time and then give up. And I know this seems lazy or greedy or something. But the point is that even getting myself to the beginning of things is so scary and tiring that if the thing doesn't turn out well, it's completely devastating. So things need to work right away.
And I think for some people, the risk that is scary/tiring can be a very small risk, as small as trying to understand what someone else is asking you to do. So, M&Ms.