Relationships are a lot of work if you want to keep them healthy and productive, no matter whether they are personal or professional. At times I have under-appreciated this in a professional capacity and let things slide. In a lot of cases the consequences are minimal, as the parties gradually drift in different directions, but in other cases there is more at stake and the relationship needs to be maintained or ended, with no gray zone.
I don't consider myself overly conflict averse but I think, like most people, I have a tendency to push addressing a conflict off when I am overwhelmed with other issues. It's not the right strategy because the conflict looms and rarely resolves itself when ignored, but it's easy to say "I can't deal with that right now". Eventually, however, the situation while rear its ugly head and often need to be dealt with at the least convenient time possible.
One thing I feel I really need to work on as a PI is recognizing bad relationships early on and dealing with them at that time. While it sucks to professionally "break-up" with someone, it ends up being infinitely better for both parties in the end, rather than dragging out some extended and overly dramatic crawl to the inevitable.
Sometimes a relationship just isn't good for two parties and it's time to move on.
And it doesn't even have to be because someone is ill and you have a younger model waiting in the wings.