The ending was the saddest part. After all the hardships and sacrifices of Feng Wu and Jun Lin Yuan for their love story, they will have to be apart as Feng Wu/Meng Yuan doesn't really belong there. Three years ago, the real Feng Wu died and Meng Yuan's spirit was transferred in Feng Wu's dead body. During Feng Wu and Jun Lin Yuan's conversation, "I can't remember which episode was that", she told him that she will have to go back to where she belong. This is a sign that in the end, when she accomplished her mission, she will have to leave. I don't know if you would agree with me, but I realized that Mu Jiuzhou actually died in the last episode when he gave the entirety of his remaining spiritual power to Jun Lin Yuan. Before the wedding of Feng Wu and Jun Lin Yuan, Mu Jiuzhou came to pick her up to take her where she belong - the afterlife. The story ended with Feng Wu's last words, 'This is the story of my second life. Don't care too much about how it ends. The most important thing is that we've experienced, grown and loved.' These final words meant the end of her second life.