Things you just never do in battles.

[caravel]

How many times have I done that? It takes a lot of restraint and forsight to know when the rout is for real. I have often had my exhausted heavy cav surprised by rallying units and/or reinforcements at the other side of the field and utterly destroyed. When in critical defensive battles I tend to avoid pursuing routers all together and set my whole infantry formation to hold position, preferably perched atop a hill. This prevents them from following enemies of their own accord. My cavalry I hold in reserve to protect the flanks and briefly hit routers, but not pursue them.

[Lokiss]

Ugh. Likewise. Mostly trying to suppress revolting provinces with heaps of heavy cavalry (they really **** those peasants up).

[The Lizard Pope]

Fight fair with Mongols. Into the woods or over the bridge ye come....