Mother Teresa was one of the 20th century’s greatest humanitarians. But she wasn’t perfect. Just like anyone else, she had her struggles, including depression and spiritual doubt. Before she became Mother Teresa, she was Agnes Gonxha Bojaxhiu. At 18, she became a nun and took the name Sister Mary Teresa. Before long, she was in India teaching children from the poorest Bengali families. But it wasn’t until she was 36 that she found her true calling.