How do I maintain control of the fight?

So, I have played WH2 for a while and used to play Shogun2 a lot many years ago, and that’s pretty much it. How do I control the fight and not let it descend into a blob fest? This didn’t really matter for me when I played lizardmen and skaven as they are carried by huge buffed melee+good arts and weapons teams respectively, but when I started playing cavalry-reliant or micro intensive factions I ran into a problem of losing control of the fight. Sometimes my cavalry gets sucked in by an infantry unit, or my infantry can’t reach anything because it’s bodyblocked by random skavenslaves. I see people here talking about things that are yet ungrasp-able for me, like picking out some units or cycle charging. Is there a special way to practice this or some tips on controlling the units?