A trip to Mars won't be like taking a short cruise with artificial gravity so you can feel the Martian sand between your toes and relax while watching the Martian sunset.
It would be a months-long journey in zero gravity and, once you get there, you can only be on the surface for a short time in a cumbersome environment suit before you have to shut yourself away in a base. Even making the journey would be physically taxing, requiring you to not only be very physically fit but specially trained to work in low gravity environments.
While there, it would dawn on you the gravity of having no straightforward way off the planet or outside of your base. You end up trapped in a tiny station composed of cramped metal tubes that only feels smaller every day with people who are slowly outstaying their welcome.
The few times that you're able to get outside in your bulky suit, whether you're on the moon or Mars, you would look around to see that everything in every direction looks exactly the same. Of course there are a few landmarks you can make out and there is some heterogeneity in how big or small the rocks are beneath your feet, but it's mostly a single color composed of a single material.
The likely outcome from living in this state of isolation is insomnia, homesickness, cabin fever, prairie fever, a decline in cognitive ability, and increasing emotional numbness. You begin to lose your sense of self and your sense of time. You would eventually forget what fresh air was like.
Your body, too, would begin to break down with your mind due to the alien environment. Your muscles would atrophy, your bones would go weak, and your blood would thin. You would begin to feel sicker and sicker alongside your growing madness.
I think it would change most people. It would make them more detached and apathetic, perhaps even more pessimistic and cynical.
