You are baking a cake. You have all the ingredients. The tools required. The oven. The time. You promise others a piece of the cake.
Someone asks you "how long will it take to bake the cake" and you answer "we'll see what happens"!
WHAT?
YOU are the one who promised the cake. YOU are the one with the ingredients. YOU are the only one who can control the outcome. How can you say "we'll see what happens" and NOT be a complete and utter blithering idiot? How can you NOT KNOW WHEN YOU ARE IN COMPLETE CONTROL?
Of course I am NOT talking about a cake.