The misconception that the earth is a unique biosphere that humans are limited to, and that nature readily presents us with all our needs (food, shelter, water, etc).
In reality earth never had our priorities in mind. Since the earliest times we had to create technology to survive. Even today, without such technology, we would only survive a few hours in say Oxford's winter.
So you are already an astronaut. Your condition is as precarious as that of the people in a well-established colony on Mars who can take certain technological advances for granted. And there’s no reason to think that such a future beyond Earth does't await us, barring some catastrophe, whether of our own making or not.
Technology, once created, is automatic. We don't have to think about it. Take your shirt for instance. Once fabricated it warms you ever-day; it's not something you have to configure every morning or devote any mental energy towards.
The reality is, with the right knowledge, we could survive in almost any part of the universe. Not only survive, but thrive, creating a beautiful environment perfectly tailored to our requirements.
Even in completely empty areas of space we could feasibly build a space-station by hoovering up hydrogen atoms (which sprinkle the universe), transmuting them into the materials we'd need.
Such space-stations could then perform experiments based on the physics of the area and the 'evidence' streaming in from starlight, creating more Knowledge and expanding People's impact on the universe.