Hello! 

As with the new Goblin drama coming up i am kinda hooked on the plot of it and curious if there are any similar drama out there?

With that i mean with an immortal main character or nearly impossible to kill, and with him/her falling for a human:D 

It can be korean, chinese, japanese or taiwanese, and any time period!

Btw no vampire dramas seing as I've checked out most of them already.

Similar dramas that I've already watched:

Behind your smile

Blood

Gu family book

My girlfriend is a gumiho

My amazing boyfriend

You who came from the star

My drama list: http://mydramalist.com/dramalist/Krispey (Yes i have dropped many good dramas halfway, just deal with it >:D) 

Wu Xin: The Monster Killer
She Is 200 Years Old
Angel Destiny
Ruk Mai Mee Wun Tay

Not very good drama, but have this theme:
Secret Angel
A journey of flower - Chinese drama. Plot sounds lame as it's slow to start but it's honestly good. It may differ from your original question in some ways. I've added the difference as a small spoiler so read on if you want (highlight the bit after this). The main female lead isn't technically human as later on she becomes possessed. The man male lead is almost immortal but would have to take one hell of a beating.Oh and the dubbing is totally cr@p especially if you have seen Huo Wallace in things like love me if you dare. You do get used to it.
Tyvm guys! I'll check them all out later :D 
Still not sure how Behind Your Smile fits in to this theme.