Against the Odds
If a session ever went 100% how I expected and completely according to both my plan and the players, I think my brain would cease to function. The infinite improbability required for things to go that smoothly would obviously be balanced by crippling ill fortune afterwards potentially involving either car crashes or spontaneous bowel distress.
For me, its not about planning a story, but planning for the mind set. I have become good at profiling my players. I can make a choice, see the valid arguments, and contemplate the outcome without ever hitting the table. Then when we do, it usually goes how it went in my mind. Occasionally its gone different, one player decided to go against the rest of the party, and chose to not go with him. His character got killed in the middle of the night, cause he was too close to the bad guy, who was faking being a cleric npc in the party. When she had to leave, he refused to go with the others cause she had healing powers. It wasn’t a month later they all found out what happened in game.