For some odd reason, whenever I'm in a group and we're doing poorly enough for someone to get angry and quit, when the replacement shows up everything winds up going more smoothly. This isn't some case of "Well the person who got angry was clearly the problem." Sometimes the problem is me having a rougher go of it than normal, sometimes it is someone else, frequently it's because someone lagged on Titan and got tossed off the platform, someone gets angry an leaves, we get a replacement and tear the duty apart. Maybe the failure that resulted in the person leaving sharpened our resolve or something.

More on topic, I never leave a duty, largely because I'm too stubborn to admit defeat ((I'm the type of person who'll get my rear handed to me in a classic RPG and lose an hour or two rather than use the run option.))