It would be pretty awesome if we all had plenty of mental energy to stay motivated and disciplined all day long, to be highly productive and highly creative whenever we needed, and to always feel vibrant and optimistic about the future.
However, the more you try to control elements of your life – whether it is to improve your health, wealth, social life or whatever – the more apparent it is how finite and scarce this “mental energy” can be.
In particular, it seems that whenever we use willpower – in any form and for any reason – we are using up resources from this pool of mental energy, much faster than the pool is replenished.
Psychologists have carried out plenty of experiments that strongly appear to confirm this model of willpower – Jason Shen and Sebastian recently put together a great post about it here: http://sebastianmarshall.com/developing-willpower-by-jason-shen which is very much worth reading if you haven't already!
Psychologists have also shown that decisions on matters that affect us can deplete the same mental resource as willpower. In some sense, these decisions and willpower are the same: