It's where the ability to read a game comes into play, as well as recognizing good ball vs slow ball.
From set pieces, all 15 on the pitch know what will happen as forwards are taught the moves, it means you can almost guarantee quick ball for second phase, especially if you keep it within the 10/12 channel. Managing a game of rugby from 10 is like playing chess, you have to play certain moves in order to create alternatives later in the game i.e: Attacking down 10/12 will draw defenders in narrower, then means more space in the second half out wide if they all start crabbing. Remember to listen to your 9 and 12, you want your 12 to be your second set of eyes out wide and even let him tell you what move he fancies.
You'll get the hang of it, try training in a highly pressurized environment, it'll help your decision making and game reading.