In relationships that matter to me, I have no reservations about necessary confrontation. Pretending that everything is fine, when it actually isn't, is disingenuous and just puts off the inevitable. Sweeping an issue under the rug only means it will likely bubble up somewhere else instead. While these conversations can get heated / emotional, they're an integral part of the healing process and ultimately strengthen my relationships. But, these conversations are only effective when they take place at the right time and place.
If I have a lingering feeling that someone may opt to end a relationship, instead of trying to fix it, then I need to consider whether that relationship is worth salvaging. When people truly care about each other, then each person appreciates that the other person feels comfortable bringing up unpleasant topics in hopes of reaching deeper understanding.