1. do your exercise or you will fail the exam.
-> If you don't do your exercise, you'll fail the exam
2. Save some money or you won't able to buy the house.
-> Unless you save some money, you'll able to buy the house
3. behave yourself or your parents will be very unhappy.
-> If you don't behave yourself, your parents will be very unhappy
4. do it carefully or you will feel sorry afterwards
-> Unless you do it carefully, you won't feel sorry afterwards
5. Ask him first or he won't offer to help.
-> If you don't ask him first, he won't offer to help
6. be calm or you'll make a wrong desicion
-> Unless you are calming, you'll make a right desicion
7. be careful or you'll cut yourself with that knife
-> If you aren't careful, you'll cut yourself with that knife