Psychology is necessary for interstellar travel.

"As above, so below"

Let's start from the largest unit: the entire human species.

Prehistory was our infancy, prioritizing survival over everything else. Ancient civilization to the Age of Discovery was our childhood. We moved past survival and into exploration. The Enlightenment to the modern era is humanity in it's tweens. We're taking what we learned and are starting to refine it.

Humans have just completed the foundations needed before even thinking about space travel: organized society, advanced technology, and globalization. Through these we've figured out how to efficiently fulfill our basic biological needs. But here's the problem—we still blow each other up like little children fighting.

Corruption, greed, prejudice.

These awful acts and many more hinders our advancement. We have the brains and the technology to go to space, yet we're too busy pulling each others' hairs on this floating rock. To go past our solar system, social cohesion and some form of world peace is a necessity.

Let's zoom down into the smallest unit: a single person.

I believe that in order to progress, society needs to recognize the overwhelming necessity of psychology. Like animals in zoos developing zoochosis; we aren't made for modern life. The current and prevalent structure of it goes against our very own biological processes. Pair that with a lack of societal recognition for mental issues and no wonder there's a mental health crisis.

We're a conscious species that developed deep emotions and feelings, yet we don't prioritize it—much less recognize it—as something needed to be worked on.

If we want to manage the entire population, we need to know how to manage our own impulses, stresses, feelings, and behaviors. Values and emotional maturity reflect even in the largest groups of people.

Healthy or unhealthy: thinking habits and ways of expressing them continue generation after generation. I see videos of parents who teach their very young kids emotional regulation and proper communication of emotions, and the comments are always filled with amazement on how the kid didn't lash out or throw a fit. That behavior shouldn't be an outlier, it should be a standard, and it's saddening that it isn't.

There are so many bad mentalities today that are built from our monkey brain mechanics prioritizing the amygdala over the prefrontal cortex (+ them becoming societal norms which amplifies them), and the underdevelopment of and lack of teaching for emotional regulation and awareness. Toxic masculinity, misogyny, Us vs Them, bigotry, obsession with status, inability to take rejection or opposition, egocentrism, the list goes on—it's the reason why we can have the smallest conflicts with our friends to countries at war.

Tldr: A lack of mental health support and the inability to emotionally regulate and communicate with EQ creates susceptibility to division among people, leading to conflict. Union is necessary for technological advancement.

Note:
I'm a kid who knows nothing and just thought this up at 3 am. I'm most definitely biased to psychology because I'm interested in pursuing it along with neuroscience.

One more interesting thought that probably ventures into fiction:

The human mind could evolve in three ways:

1. Idiocracy Route. Consumerism takes over and the perils of modern life are too much to handle. We just laze around all day and our logical abilities shrink

2. Developmental Route. Psychological care availability increases and humans manage their minds to work with modernity and develope healthier lifestyle systems. Eventually human evolution catches up and humans become egoless. The prefrontal cortex expands.

3. Apathy route. If suicide rates increase or plateau at a high number over millennium and mental health resources remain unavailable with few secondary help options, natural selection can take over and create humans with no feelings or empathy. The logical part of our brain continues to develop but our emotional capacity shrinks to zero. Could be argued that this can't happen because we need it to collaborate and create things, but ants do it just fine without them. We could become soulless flesh bots.