-When you get into a fight that you know you cannot win and you cannot run, use the main body of your force to attack the enemy and have ranged units fire at them. Slam your cavalry into the rear of the enemy, then pull them away again. Repeat this and you can at least cause the enemy to lose as much of his forces as possible.
-When starting battle that you cannot win but you have dogs, let the dogs on the front of the main force of the enemy. Retreat your troops. The dogs will still attack and kill plenty of enemies, without losing soldiers. The dogs are fast and hard to kill. After the battle, attack the enemy. If you are still outnumbered, purchase mercenaries. The enemy will now have less troops than you. Of course, you can still attack with your main force when all the dogs are dead.