When I travel abroad, I make sure to bring my passport and a copy of passport, a multi adaptor for travel and some cup-ramens.
First, I need my passport to get on a plane and enter a forgien country.  I also prepare a copy in case of emergency such as when I lost mine. Second, a multi adaptor is a must have item when I use electronics in other country because the electricity in each country is different. Finally, I bring enough cup-ramens to last me a few days. It is very helpful when I miss Korean food on a trip abroad. Furthermore, they are very convenient to carry and cook. Without them, I can't feel comfortable.