Good quotes about losing a best friend include "But fate ordains that dearest friends must part" by Edward Young and Charles Caleb Colton's quote that like true health, people don't realize the importance of true friendship until losing it. Both quotes refer to the death of a friend.
Edward Young was an English poet, and his quote refers to the inevitability of friends leaving each other due to death. Charles Caleb Colton was an English author and clergyman. Although quotes about the loss of a friend are often about the death of a friend, many are about friendships ending or friends growing apart. While a friend dying typically causes sadness, a broken friendship often causes regret.