Unravelling the complexity of human development is a daunting task and it is unlikely that scientists will ever be able to do so for even one individual, because the interactions of biology and environment are likelihoods and not certainties. There are just too many ways that the cards could stack up. More importantly, as the vernacular saying goes, "Shit happens", which is a very succinct and scientifically accurate way of saying that random events during development can change the course of who we become in unpredictable ways.

Ego depletion comes from American psychologist Roy Baumeister, who believes that enduring something stressful exhausts our capacity for willpower to the extent that we give in to our temptations that we would rather avoid.