It's not been explained clearly yet but it sounds like Jin are basically emotionless most of the time. Without true desires. The only thing that can get them to feel things is their 'hobby'. Like Captain Mi's little sister. Fangirling for the Dean xD and Yeo-dam for the Emperor
I think it means fate one or your half one , you re only one...you understand where I go
I do understand what you are trying to say but I don't think it's right cause they said the Deans hobby was fangirling over other more powerful jins. I think it's more like your reason for living. Your passion.
Personally , if it is a personwho makes you feel like that , and a reason for leaving I think it's can't be just passion ... it's love
I'm still confused what exactly is a hobby to Jin