Bit off topic but..
Ccavalry have a few roles and one of them is to counter enemy cavalry and stop them from maneuvering easily behind their team mates, once they have dealt with the enemy cavalry then they are free to attack the enemy, without worrying about being lanced.
When I play my HA I always hunt down the enemy cavalry first, I like to catch them far from the battle when they are trying to sneak around the back, if they have a shield I just shoot their horses to death and leave them to run miles, then go do the same to all the other cav, before returning to my army so I can pick off any enemies that come near the flanks or their own flanks.
On my lancer I move with my force, engage enemy cavalry that attacks and then break off once the main force engage, so I can outflank the enemy.
Taking out enemy cavalry is important regardless of whether you're on a horse or not, countless times has a lone cavalryman repeatedly charged through the back of the force killing multiple people, whilst no one seems to take much notice of him and end up getting backstabbed by him too.