V-아/어야지(요) grammar = will do, must do ~express strong intention or decision to do something

V-아/어야지(요) grammar = will do, must do ~express strong intention or decision to do something

Usage:
- V-아/어야지(요) is used to express speaker’s strong intention like a promise to oneself or a decision to do something = will do, must do

- V-아/어야지요 can be shortened to V-아/어야죠.

- When speaking or thinking to oneself, informal form V-아/어야지 is used.
- When scolding someone gently for not doing something they should do, V-았/었어야지 is used.

- V-아/어야지 also has a completely different usage. When it is used at the middle of the sentence, it is used to express a condition to realize something. 

See: V-아/어야(지) grammar = (have to) do A, so B can 

Tense:

Verb + -아/어야지(요).  (positive form) = must do, will do
가다 -> 가야지요. / 가야지.

보다 -> 봐야지요. / 봐야지.

먹다 -> 먹어야지요. / 먹어야지.

지키다 -> 지켜야지요./ 지켜야지.

빼다 -> 빼야지요./ 빼야지.

합격하다 -> 합격해야지요. / 합격해야지.

공부하다 -> 공부해야지요. / 공부해야지.

Verb + -지 말아야지(요).  (negative form) = must not do, won't do

보다 -> 보지 말아야지요.

자다 -> 자지 말아야지요.

만나다 -> 만나지 말아야지요.

지각하다 ->  지각하지 말아야지요.

Examples:

1. 그 영화가 너무 재미있다고 했어. 나도 봐야지.

I heard that the movie is very interesting. I will see it, too.

2. 이렇게 자꾸 지각하면 큰일이야. 내일부터 절대 회사에 지각하지 말아야지.

I will be in a big trouble if I am often late like this. Starting from tomorrow, I won’t be late anymore.

3. 한국어로 내 의견을 잘 표현하고 싶어. 올해는 꼭 TOPIK 6급 시험에 합격하야지.

I really want to express my opinion well in Korean. This year I must pass the level 6 TOPIK exam.

4. 요즘 배가 많이 나왔네. 올해는 꼭 뱃살을 빼야지.

My belly became much bigger. This year I must reduce my belly weight.

5. 일이 잘 될 것 같지 않은데 시작했으니까 꼭 끝까지 해 봐야지.

The work is not going well, but I have started it, so I must do it until the end.

6. 나중에 공포 영화를 보지 말아야지.

Later, I won't watch horror movies anymore.

7. 몸이 안 좋으면 무리하지 말고 쉬었야지요.

If you weren’t feeling well, you should have rested instead of pushing yourself too hard.

8. 한국 회사에 일을 하려면 일단 한국어를 잘해야지.

If you want to work for a Korean company, you must speak Korean well.

9. 과학자가 되려면 일단 공부를 잘해야지. 

To become a scientist, I must study well first.

10. 고기만 먹지 말고 채소도 먹어야지. 

Don't just eat meat, eat vegetables too. 

11. 피곤해도 양치 하고 나서 자야지.  

Even if you're tired, you must brush your teeth before going to sleep.

12. 아기가 자고 있는데 좀 조용히 했어야지.

The baby is sleeping, you should have been quiet.

13. 고향 음식이 너무 먹고 싶다. 다음 방학에 가서 엄마가 해 주신 음식을 실컷 먹어야지.

I really miss my hometown foods. I will visit my hometown in the next vacation and stuff myself with mom’s cooking.

14. 작년에 교통 신호를 어겨서 벌금을 많이 냈지요?

- 네, 올해부터는 교통 신호를 잘 지켜야지요.

Last year you ran a traffic light and paid a big fine, right?

- Yes, from this year I have got to obey traffic signals.

15. 세미나가 꼭 가야돼?

- 그럼요. 우리 선생님이 발표를 하시니까 꼭 가야지요.

Do we have to attend the seminar?

- Of course, our teacher is giving a presentation, so we have to go.