"You are not entering this world in the usual manner, for you are setting forth to be a Dungeon Master. Certainly there are stout fighters, mighty magic-users, wily thieves, and courageous clerics who will make their mark in the magical lands of D&D adventure. You however, are above even the greatest of these, for as DM you are to become the Shaper of the Cosmos. It is you who will give form and content to the all the universe. You will breathe life into the stillness, giving meaning and purpose to all the actions which are to follow."
- Gary Gygax (Co-Creator of Dungeons and Dragons)
When you think about becoming a Dungeon Master, you may not consider all that you have in your control. You are the one who determines the reaction of the Cosmos to whatever happens in your game. Does the death of an enemy create a rift between factions within the world? Does the party's choice to delay visiting a town mean that town's demise? Does the butterfly effect exist and does it occur?
All these things can and should be considered when determining which way a story goes and can create some interesting elements in the game that previously weren't there. For example, your party chooses to explore a cave that they were ambushed from in order to ensure that no one gets ambushed by any stragglers in the cave. The cave continues farther than they expected causing them to spend an additional day exploring and clearing out the cave.
This choice could do any or all of the following:
- Caravans are able to get through without being ambushed therefore supplies and trade are uninhibited.
- The town the party was headed to has had an unfortunate event happen that could have been prevented potentially if they were there to assist.
- The bandits that were ambushing and escaped the party report back to the leader and now the party is being targeted.
- The party discovers an artifact that isn't useful now, but could potentially be used as a plot device later.
All these options are just a few examples of what could potentially happen because of a party's decision. The only thing holding back these events from ensuing is you as the DM. If you 'breathe life' and 'give meaning and purpose' to the event, you can easily incorporate it.