I took my umbrella, but it wasn't raining.
I needn't have taken the umbrella.
I bought the meat, but I didn't have time to cook the dinner.
I needn't have bought the meat.
I went to work earlier, but nobody was there.
I needn't have gone there so early.
It was my free day yesterday, so it wasn't necessary for me to go to work.
I didn't need to go to work.
My mother cooked the lunch, so it wasn't necessary for me to cook the lunch.
I didn't need to cook the lunch.
My friend gave me a lift, so it wasn't necessary for me to call a taxi.
I didn't need to call a taxi.
I took my camera with me, but I didn't have time to take any photos.
I needn't have taken my camera with me.
I had a lot of food at home, so it wasn't necessary to go shopping.
I didn't need to go shopping.
I don't know why he came. He could have just called me.
He needn't have come.
We booked the table, but the restaurant was empty.
We needn't have booked the table.
