Many of us will start 2016 with resolutions – to get fit, learn a new skill, eat differently. If we really want to do these things, why did we wait until an arbitrary date which marks nothing more important than a timekeeping convention? The answer tells us something important about the psychology of motivation, and about what popular theories of self-control miss out.
You could see these contradictions as failures of our self-control: impulses for temporary pleasures manage to somehow override our longer-term interests. One fashionable theory of self-control, proposed by Roy Baumeister at Florida State University, is the 'ego-depletion' account. This theory states that self-control is like a muscle. This means you can exhaust it in the short-term – meaning that every temptation you resist makes it more likely that you'll yield to the next temptation, even if it is a temptation to do something entirely different.