Okay, first and foremost, I AM NOT A CRITIC. I just love the story of this series and I am forced to write my own reaction.
I just saw this series, the whole 108 episodes of it. At first, I just thought that this is just some plain love story between a General Manager and a newbie employee who both fell in love along the way. But watching the series, I discovered that it was more than just a love story. It was a story about a mother’s love. Not just your biological mother, it also includes an adaptive mother, your mother-in-laws, the grandmothers, soon to be mothers. I was a bit crazy to think that just because it says “Mother of Mine”, the newbie employee thinks of his girlfriend as his “mother”. My bad about that. Mother of Mine  or My Prettiest Daughter In The World (literal title) is GOOD.
Anyways, the series has a whopping 108 episodes. Enough to make you busy for 4-5 days during this quarantine period. Korean series just take around 16 to 20 episodes, which is the typical length. The most common length of a Korean drama is 16 to 20 one hour-long episodes, or a total of 16 to 20 hours of content that are broadcast for 8 to 10 weeks (around 2 months). When you do the math in terms of 30 minutes-long running time, you get 32 to 40 episodes. In any case, each drama has a running time of around 60 minutes (excluding ads) every broadcast night.
In sum, most Korean dramas have 16 to 20 one hour-long episodes (cable TV) or 32 to 40 half-hour-long episodes (terrestrial TV) that air for 8 to 10 weeks There are dramas with only 12 (Voice 2), 8 (Lingerie Girls’ Generation), and 4 (The Most Beautiful Goodbye In The World) hour-long episodes. On the other hand, there are those that are so long it took 6 months before they ended such as Six Flying Dragons and Jumong with 50 and 81 hour-long episodes, respectively. 
The story is centered on Park Sun-Ja the mother, Kang Mi-Sun the eldest daughter / banker, Kang Mi-Ri the adapted / 2nd daughter / General Manager and Kang Mi-Hye the youngest / writer. I will try to give them a brief introduction but will avoid being a spoiler.
I love how the story was made. Kang Mi-Sun the eldest among the three is also a mother to her young daughter. Married to a sleazy guy who loves his toys, literally. He has Gundam toys, trains, VR goggles, a bike, fishing rods, and a lot more. But in the end, he became a changed man and redeemed himself.
Kang Mi-Ri is the second of the three sisters. Ambitious, serious, driven. She was left behind by her biological mother who turns out, is just nearby her.
Kang Mi-Hye is the youngest and a writer.
The lesson is very simple but also a bit complicated. Love, forgiveness, healing of the past hurts, moving towards the future, being brave. You pick any of these and it’s there. The series aired from March 23 to September 22, 2019.
You can watch the series on YouTube.
 Mother of Mine – AsianWiki. (n.d.). Retrieved May 3, 2020, from http://asianwiki.com/Mother_of_Mine
 S. (2019, April 18). You’re NOT an avid Korean drama fan if you don’t know these facts. Retrieved May 3, 2020, from https://www.kdramapal.com/youre-not-an-avid-korean-drama-fan-if-you-dont-know-these-facts/