Use this phrase to show that you had different expectations that were not met. We lost the game; so much for our unbeatable streak.
Pro Tip 2/3
Irony or Sarcasm
This phrase can carry a sarcastic tone when the outcome is opposite to what was assured or expected. You said traffic would be light today, so much for your traffic forecasts.
Pro Tip 3/3
Cancellation Implication
Implies that plans or expectations have been cancelled or rendered moot due to circumstances. The lead actor got sick, so much for tonight's show.