In the case of writing, I've moved from the usual story telling with lots of action, and I've been dwelling a lot on the character's inner thoughts/reflections/struggles. I find greater pleasure in delving into the person's depths - carving out the identity, the emotions, focusing on how the individual reacts in a certain situation - rather than weaving out the actual plot or creating dialogue, which can be quite unfortunate since most readers like action-based stories. I'm not sure when I went from Point A to Point B, but it's harder to write all those sweet, light-hearted stories now. If I do write any. They all now tend to turn out as serious, life-searching, monologue-type fiction. Maybe it's an INFJ thing, or maybe it's just the quarter-life crisis stage I'm at. (I hear INFPs like writing dialogues whereas INFJs prefer monologues, but I can't be certain.)
The digging for information/reading up on issues of interest/getting fixated on seemingly unrelated topics and obsessively trying to find out all about them, it's been there ever since i can remember. I've never been able to explain why I get so 'zoomed in' on a specific topic or character and can spend hours learning about it. ( get that others get fixated on stuff as well - hobbies, careers, celebrities, etc) For me, it begins with this insatiable need to learn, to keep improving, to make constant progress, as a person. And sometimes it goes overboard. That's when I've to pull back and tell myself to chill.