Once you come to realize that all material possessions and earthly things will burn away, it changes your perspective. The world thinks that this earthly life is the sum of our existence and that everything within it is the sum of our reward. Based on that understanding, everything we do on earth matters in a way that has us pursue as much gain, reward and satisfaction as we can because one day, it will all come to an end.
The Bible is full of stories of men and women who were called by God to do difficult and even impossible things and found God to be sufficient.