I wish I had booked a room.
If I had booked a room, I would have somewhere to stay.
I wish I hadn't eaten so much chocolate.
If I hadn't eaten so much chocolate, I would't feel so ill.
I wish I hadn't touched the iron.
If I hadn't touched the iron, my hand wouldn't be hurt so much.
I wish I had gotten up earlier.
If I had gotten up earlier, I wouldn't be late now.