While thinking about warcraft the other day, I had a realization. In a WarCraft III game, as any moderate player or above will tell you, its all about depriving the opponent of resources, making sure he loses more resources then you do. Thats why you micro so hard in battle, so you don't lose units. Thats why you have your build order, so you make sure no one has a better start then you, so you can have just as many resources. Thats why you don't scroll of mass teleport a level one hero when it gets surrounded. Its better to let it die, it costs less resources. It goes on and on. Decisions you make to kill his units more effectively, (every decision) are to deprive him of resources.
Now lets look at another part of the game, nearly as important as hit points. Mana. Now, mana regenerates. It takes one thing: Time. So, when you cast a spell on your opponent, you are investing time. Your saying, Ňok, I want to use that 40 seconds my Archmage spent regenerating mana and use it to cast a water elemental, not use blizzard.Ó So is a water elemental worth the investment of the AM?
Now, what did you invest in the Archmage? If it's your second hero, you invested 425 gold and 100 lumber. You also invested a farm that costs eighty gold and 20 lumber. What do you need to get 505 gold and 120 lumber? Time. Everthing in warcraft is a function of time. How much time do you need for X resources? How much damage does a footman do in so many seconds compared to a grunt? An archer? A ghoul? What do you need to do damage at all? What do you need to use a scroll of regeneration? What do you need to use healing salve? What do you need to revive your hero? What do you need to get resources? What do you need to move units? Time.
Time. This is what makes instant damage spells so good, they need zero time. Spells like entangle are very much like this too, they force their own time, overriding the player. The only way to combat instant damage spell is with no time. The only way I can't cast storm bolt on your hero is if it is within range exactly never. Also, how long does it take to use a healing potion? No time. What do you need to stop him from using a healing potion? Kill his hero. Now he has no time again.
All the pressures of being able to play well mean doing more in less time. This is what makes speed so good, its like your opponent is moving in slow motion. Good luck using your time!