I was really shocked how similar I found those two titles.
Not by story, but by aesthetics.
I thought, I was convinced, that those titles are connected by the same director and yet I was wrong which is amazing.
Still I think that JBL has better acting and music than DAYS (hehehe I just did ‘days’ while typing the shortage of the title, lol).
Yeah, but the vibe in DAYS is like mix of JBL and Goblin.

If you're looking for beautiful (and funny) friendship between people who are supposed to be enemies you should try it.
MS is historical drama while Goblin has only historical retrospections.

Both have sweet relationship based on female-chases-male-first and him being cold and distanced when she's cheerful and cute.
Except in Goblin we have a teenage girl when in FMIYM we have all adults.

I think that the delicacy and pace with which the main character's relationship develops is similar, so if that's what you've been captivated by in one of these titles, the second one can also appeal to you.
It is worth mentioning that both are well-directed - with particular emphasis on details - which I think is a very strong side of these dramas.
In addition, both affect the problem of coping with the loss of a loved one.

Both are about Sampoong Department Store collapse and concern suffering after the loss of a loved one.

Both having part with famous mother who cannot take proper care of her newborn baby because of fear of eventual scandal.

In both dramas lead female character is quite unsexual (at the beggining) and is trying to find her womanhood with a help from a guy.
In 'Personal...' the lady is clumsy, soft and cute while in 'Witch...' the lady is cold, dark and arrogant.