This really is a hard question to answer.. I'm gonna tell you what I feel about those words.. I don't know how it is for other koreans though. Someone might say otherwise.. 지금 vs 이제 지금has more of 'right now' meaning, like a pin-point in time. 이제 has a little bit more future-showing kind of meaning. So.. when you say 지금, it means 'now,' and 이제 has just a trifle more relation with the future, at least I think so. But it's very subtle and I think there might be some koreans who would think them just same. 걱정 vs 고민 I think 고민 is more troubling. Just a bit stronger in its degree. 금방 vs 곧 금방 미국에 돌아가요 sounds wierd. I guess 금방 is more near-future than 곧. I think you can translate 금방 ~해요 into 'about to ~,' and 곧 into 'soon.' Hope this could help