For what it's worth (limited, I know), my experience with (competitive, non-staged) reenactment combat is that ...

1) it's bloody difficult to disengage successfully unless you are winning (which means you have a numerical advantage -mates to cover you- or a psychological advantage -the enemy is not prepared to give chase- or both).

2) because we're not using sharp weapons, we don't generally break and run. However, I have learned to identify the 'break point' -the point where one side would have broken were we actually fighting. Unless there is a flanking attack, it generally occurs just after one side loses formation and the enemy manages to exploit this successfully. This means getting a series of two (or more) on one, blindsiding or just engaging unready opponents as chaos erupts. If successful, this causes massive casualties to few in return and is near-impossible to recover from. At this point dropping your weapon and running is your best chance, but of course we don't actually do that.

The chaos just after lines are broken is where most get killed. Chasing someone who runs full tilt is not attractive, because you have to do the same and so if he turns on you, you have lost your tactical advantage. Unless you are cavalry, of course, and can run him down without losing combat-readiness.

Not saying I'm an expert in combat psychology, just my 0.05$ from slightly relevant experience.