This is by far my favourite drama, so overwhelming and meaningful.

Story
This is basically the story of broken people who try to heal each other. The trauma they had in their childhood still have vivid consequences in their adult life. It's not only a romance, it's not only a medical drama, it's both and so much more. The dialogues are so well-written and life-changing (and I don't even exaggerate).

Acting/Cast
The relationships between the characters are perfectly led. Mother-daughter/mother-sons/brothers/lovers/friends/colleagues every relationship is relevant and show the importance of social interaction on the way to overcome a trauma.
Heads down for the whole cast. Gong Hyo Jin & Jo In Sung are incredible but let's not forget the other actors who give a great dimension to their characters. Everyone is endearing and you just want more of them.

Music
Meaningful -- the songs fit the story and you will probably tear up listening to it later.

Rewatch value
I watched this drama in 2014 when it was released and again last month, it never gets old. I liked it even more this time because despite knowing all the plot twists, I still get surprised. I am 6 years older and mental health is much more meaningful today for me than it was back then.

Give it a try !!