"Continuously experting self-control, resisting temptation, and 
delaying gratification can be depleting, with deleterious 
consequences for attention and performance. We might expect the poor, 
with their lack of slack and a recurring need to show restraint and 
resist temptation, to be chronically ego depleted. Both poverty and 
the instability it brings deplete self-control, making saving, 
planning, and coping with unforeseen events especially challenging. 
Highly constrained financial resources and a lack of slack require 
constant budgeting vigilance, resistance, and delayed gratification, 
all of which drain attention and self-control and further diminish capacity. "

Mullainathan and Shafir in Shafir, Behavioral Foundations of Public 
Policy, 2013, p 283

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