Here's a great exemple of how ruin a great drama. It begins to go downhill already, around 15-16th, but after 20th episode, seems that someone else has taken the writers' place.
I rewatched a couple of times and I always love the first half of the drama. Their chemistry and acting is so natural, really few dramas have achieved that. Also, their relationship grows so smoothless and they are so funny to watch.

The main problem of this drama, apart from having the most annoying second leads (both male and female), who really don't know what the word NO means, is the complete change of FL's attitude. The drama become just a misunderstanding after another and kind of depressing. There are really few more great laughs in the second half of the drama.

Nonetheless, I think you should give it a try, because the first half is really worth it. Maybe you can stop around 20th episode, thinking of that as a proper ending.