"Obstacles are the things we
see when we take our eyes off the goal" -Henry Ford.
Firstly, people don't
want to change. They're happy the way they are. The ones who are
actually motivated to change don't wait until new years. They don't need
a specific day to start their transition. If somebody really wants to
change, then nothing will get in their way.
"Normally if
given a choice between doing something and nothing, I’d choose to do
nothing. But I would do something if it helps someone do nothing. I’d
work all night if it meant nothing got done." -Ron Swanson.
Secondly,
people are lazy, they're not bothered putting in effort. Change takes
time, and time is something people don't want to spend. Unfortunately you can't instantaneously change something about you, things that you have
become accustomed to. And after putting in effort for a few weeks to change it kinda sucks and you realise what a mission it actually is. So people start convincing themselves that their
decision to change is actually not that important. A theory to which
social psychologists refer to as cognitive dissonance."Never put off till tomorrow what may be done day after tomorrow just as well" -Mark Twain.
Then there's those people who can't even get started. These people fail in understanding the notion of time. The procrastinators. I mean, they have a whole year to fulfill their new years resolution. So what's the hurry? On top of which, there probably aren't any huge consequences if they don't end up starting, because hey, there's always next year. This can generally be explained through the theory of temporal discounting. This is where, as the video explains, people 'discount' the value of the reward depending on how far away the reward is.
Of course, there's many, many more reasons why new years resolutions never seem to work. But in the end, it's not only because humanity is a complete failure, but it's also partly because that's just how the human mind works, and the only way to change it (in my opinion) is to educate ourselves and find ways to manipulate how we think about what we think. If that makes sense.