There are a lot of ways to die in Westeros. Typically, it's in some unfortunate violent matter but for Jorah his death may be caused by Greyscale, a deadly disease that kills its victims slowly. In Season 6, Daenerys commanded Jorah to find a cure for his disease so he could be by her side when she took back the Iron Throne. So how do you cure Greyscale on Game of Thrones? Unfortunately, there isn't a cure... yet.
Greyscale is a skin disease that kills off the flesh, leaving the skin cracked and flaking and eventually causing it to become stone-like. Children can sometimes survive the disease, like Princess Shireen Baratheon did, but their skin will forever be marred by the diseases effects. However, they can never contract the disease again, becoming immune to it.
Though children do occasionally survive the disease, adults are basically expected to die from Greyscale. Prior to death, the disease causes it's victims to become crazy and their skin becomes hard and dead. These people are referred to as "Stone Man" and are exiled from society.
In the books, it was stated that the symptoms of the disease could be stayed by limes, mustard poultices, and hot baths, but this only delayed the inevitable.
In the case of Shireen, and other children who survived, a specific cure was not found. It was merely a case of the child surviving the infection with the help of healers throwing everything they could at the disease until it passed. However, many fans believe Sam may have accidentally stumbled upon a cure while looking for a way to fight the White Walkers.
As Reddit user Beastmodekait pointed out, on one of the pages of the books Sam was looking at, it appears Dragonglass can be injected to cure illnesses and diseases. However, the page is cut off, so it's difficult to know for sure if that's true. Plus, even if it is, that doesn't mean Dragonglass cures all diseases.
There is good reason to believe Dragonglass is the cure, though. Shireen grew up at Dragonstone castle, where Sam has just discovered there's a whole underground trough of Dragonglass. It's possible that the Dragonglass seeped into the drinking water of those who lived in the castle and that's how Shireen was really cured.
If Dragonglass really is the cure that means Daenerys holds the key to Jorah survival. Too bad she has no idea.