Ah, I really get the engagement one. I still don't understand why you should prioritize someone over who you made your promise first, if it's not life threatening or personally damning. God, good luck with my love life lol.
And I also get Ringo's worry. In my area as well, friendships can be superficial. I've seen people change drastically and grow distant with others because of their lovers, mostly between girls. But honestly, everyone grows apart sooner or later. Simply out of the fact, it's a constant mix match of social groupings through each quarter. Asian thing, maybe? Idk.