Live as if you were to die tomorow. - This says that you should do things which you like, enjoy in life like tomorrow does not exist...everything that you want to do, do today because in future might will not be time for that.

Learn as if you were to live forever. - This says that when you learn something you should remmember it and now whole your life, not learn today and for couple of days or years forget. So we should learn something and have never forget it. It is not just about learning languages, school subjects and similar, it is also about things which we learn in life.

Hope this helps you to understand this quote better. :)