You have 100 HP and get the warning "vitals low" at ~65 damage and "vitals critical" at ~90.
There's two ways to heal damage: The ship med kit and eating roasted marshmallows. Perfectly roasted marshmallows heal you to full, so being good at roasting helps.
Easy sources of controlled recurring damage are fall damage and fire.
Combining this information, I suggest getting your suit from the ship, drop down to the campfire you start at (should get you to "vitals low"), roast a marshmallow, jump in the fire until you get vitals critical, repeat marshmallow and fire 11 times. If you lost count or chickened out before "vitals critical" once or twice, just keep rotating roasting yourself and marshmallows until you feel safe, then doze off at the campfire until the time loop ends.
If fire is too scary, or roasting perfect marshmallows too hard, 15 jumps from the tower and heals at the ship should work just as well.