Should for Giving Advice/ Expressing Criticism

We can use  should (shouldn't) for giving advice as well as expressing criticism.

For giving advice we use should (shouldn't) + bare Infinitive.

• You look tired. You shouldn't stay up late , you should have a rest.
• You shouldn't eat this hot dog: it smells horrible. You should throw it away.
• If you want to be healthy you shouldn't eat too much and you should do physical exercises.

If we want to express criticism about past events we use should (shouldn't) + perfect Infinitive

• Sam failed his exam.

        He should have worked harder. (but he didn't)

        He should haven't skipped lessons . (but he did)