Congratulations, you've finally earned your space pilot's license! The only problem is, you can't afford a large enough ship to house more than one person (considering food, breathable air, refuse recycling, etc). And the only way to earn enough credits for a larger ship is to work the cargo lanes and haul freight from one remote location to another.
This, of course, isn't the environment in which mankind evolved. We aren't meant to survive for months at a time with no social interaction.
Not getting into the tangle of Faster Than Light travel, ignoring the interplanetary economics of supply and demand, and let's not even get started on safety precautions to keep you alive in the most deadly environment known to mankind.
I want to focus on how you're going to keep yourself sane when one trip can take weeks to months at a time, with no human on board but yourself. While keeping in mind the following:
- Pets aren't allowed
- No space for humanoid robots (recharge stations and all that jazz)
- The only computer hardware on board is the NaviCom (to calculate trajectory and monitor life support systems) and a datapad.
- Installing third party AI onto your NaviCom is tricky (and illegal, but the odds of being scanned are fairly low).
- Acquiring official AI tech is so costly you might as well buy a larger ship. Monopolies are fun like that.
- Humans have not evolved much past where we are today. So long-term solitude is still damaging.
Keep in mind your focus should be psychological and sociological in nature. So working out 18 hours a day, though arguably does keep you busy, it isn't the solution you think it is.
So. Recap. You need to travel alone (for reasons, and working for someone else to save money isn't the point), and each trip takes weeks to months at a time. How do you keep yourself sane within the offered constraints?