This essay by philosopher Bence Nanay (Antwerp) makes a couple of amusing points, but I was struck by this:

[M]ost changes happen gradually and under the radar. A few mechanisms of these changes are well understood, such as the ‘mere exposure effect’: the more you are exposed to something, the more you tend to like it. Another, more troubling one, is that the more your desire for something is frustrated, the more you tend to dislike it. These changes happen gradually, often without us noticing anything.

The problem is this: if we change while our self-image remains the same, then there will be a deep abyss between who we are and who we think we are. And this leads to conflict.

To make things worse, we are exceptionally good at dismissing even the possibility that we might change. Psychologists have given this phenomenon a fancy name: ‘The End of History Illusion’. We all think that who we are now is the finished product: we will be the same in five, 10, 20 years. But, as these psychologists found, this is completely delusional – our preferences and values will be very different already in the not-so-distant future.

Why is this such a big issue? It might be okay when it comes to ordering the espresso. Maybe you now slightly prefer cappuccino, but you think of yourself as an espresso kind of person, so you keep ordering espresso. So you’re enjoying your morning drink a little bit less – not such a big deal.

But what is true of espresso is true of other preferences and values in life. Maybe you used to genuinely enjoy doing philosophy, but you no longer do. But as being a philosopher is such a stable feature of your self-image, you keep doing it. There is a huge difference between what you like and what you do. What you do is dictated not by what you like, but by what kind of person you think you are.

A number of rather serious philosophers (more serious, certainly, than the latest p-hackers in the increasingly beleaguered field of psychology) have advanced the view that character–who one is–is quite stable over much of one's life.  Schopenhauer may be the most famous modern proponent of the idea, but Nietzsche, notwithstanding the narcissism of small differences of which he was often guilty, agreed.  This passage is typical:

At the foundation of each of us, the "real bottom," there is clearly something unteachable, a brick wall of spiritual fatum, of predetermined decisions and answers to selected questions.  With respect to cardinal problems, an immutable "that I am" speaks up. (Beyond Good and Evil, 231)

The defect in the literature Prof. Nanay alludes to is that it can't distinguish between the changes that are just "noise" and those that are foundational to who the person really is.   In addition to the p-value disaster currently afflicting psychology, there really is a serious (dare I say it?) "philosophical" problem, namely, that these folks are not at all clear about what it is to be the person that one is.  They need to read some Schopenhauer and Nietzsche!