The person speaking is either speaking to someone who is leaving or speaking to someone who will be arriving soon.
Imagine these two conversations by phone:
Person 1 (in Spain) : I'm going back to Brazil tonight.
Person 2 (in Spain) : Have a safe trip back home. Hopefully we will meet again one day.
(Note, this only works if Person 1's permanent home is Brazil)
Person 1 (in Spain) : I'm coming back to Brazil tonight.
Person 2 (in Brazil) : Have a safe journey [back home]. I'll see you tomorrow!
Student or Learner