Make the conditional
I was bored so I left class.
If I hadn't been bored, I wouldn't have left class.
If I hadn't lost my phone, I wouldn't have been sad yesterday.
I lost my phone so I was sad yesterday.
My mom didn't watch tv because she didn't have time.
My mom would have watched tv if she'd had time.
If you hadn't punched me, I wouldn't have punched you back.
You punched me so I punched you back.
I didn't make dinner because there was no food in the fridge.
I would've made dinner if there had been food in the fridge.
If you'd lent me money, I would have been able to pay my parking ticket.
You didn't lend me money so I wasn't able to pay my parking ticket.
I didn't begin my homework because I drank too much last night.
I would have begun my homework if I hadn't drunk too much last night.
If the weather had been better, we could have had a barbecue.
The weather was bad so we didn't have a barbecue
I wanted to swim in the lake but I didn't wear my swimming shorts to the beach.
I would have swum in the lake if I had worn my swimming shorts to the beach.
Would you have been happy if your parents had bought you an iPhone instead of a Sony for your birthday?
Your parents bought you a Sony for your birthday so you weren't happy