“You’ve been trying not to pee in your pants your whole life,” says the retired astronaut Scott Kelly, who wore a diaper for liftoff and landing on all four of his space missions. Going into orbit will require you to confront your body in ways you don’t have to on Earth. Get over decades of conditioning by rehearsing basic bodily functions on land: Put on a diaper, lie on the floor with your legs up on the couch, and practice urinating without shame or gravity’s assistance. (Don’t, and you’ll risk damaging your bladder when your body won’t relieve itself in space.)

Leaving Earth is dangerous; you might die, and you should acknowledge and grapple with that before you go. Kelly has spent a total of 520 days in space. Before departing, he always wrote letters to his loved ones to be opened only in the case of his death. Seek help beforehand. Don’t step foot in a spacecraft without some counseling. Kelly saw a NASA psychiatrist before his missions; in space, he had biweekly therapy sessions via video chat. “You have to be strong, and stable, and grounded,” he says. Get in the habit of regular exercise and sufficient sleep, because basic self-care becomes notably harder in orbit. Work on being kind and helpful to the people around you. (NASA astronauts go on strenuous backcountry expeditions together as part of their training.)

[Read about how Scott Kelly’s body changed during a year in orbit.]

Resist the impulse to take sentimental objects along. Kelly suggests limiting yourself to photographs. “Bring as little as possible,” he says. “Dealing with stuff in space is a hassle, because everything floats.” Remember that you need to prepare your mind not just for exiting Earth’s atmosphere — and for long periods of isolation from your friends and family — but also your return to Earth, which will entail a kind of prolonged existential hangover. The longer your stay in space, the more time you’ll need to readjust. After returning from his final, 340-day mission, Kelly suffered nausea, fatigue, swelling, muscle and joint soreness, hives and rashes. It’s psychologically disorienting to suddenly go from narrow confines in which every aspect of your life is controlled back to an expansive landscape, free will, gravity and all the offerings of modern life. “You suddenly have a million choices, and it’s confusing,” Kelly says. “It’s probably very similar to what it feels like to be released from prison.”