After school I went on a 2 months travel trip with my best friend. We knew each other for 13 years, and it started really great. But after 2 or 3 weeks, we noticed that it is a difference between going to school together from 9:00 till 17:00 or staying together almost 24/7. I discovered some characteristics that I've never seen before at my friend and I think it was the same the other way round. Nevertheless we had a great trip, but sometimes, especially during long journeys or when it was necessary to make a important decision we were really annoying each other.
So my question is, what techniques are there to avoid annoying on another when staying together 24/7 during a long travel trip?