Leaving is easier when you have a return ticket.

You leave anyway, obviously, but somehow it helps to know that in x months you are going to go back home. When you feel homesick you can look at the calendar and count the days until you can see your family and friends again. When you leave without knowing when you will return, you lose that supporting comfort and even if you know you're going back someday, it's like it'll never come.

This is from the person who has just left, so I don't even want to know how I'll be in two months, when it's Christmas and I'm here alone.