♦ Here you are telling someone that you feel strongly about doing a particular action.

Examples:

1. I think I should practice my reading.
2. I think I should join a study group.
3. I think I should handle this as soon as possible.
4. I think I should earn my degree.
5. I think I should explain myself.

► By adding the word 'don't' you have changed what you are conveying from something you are thinking of doing, to something you are against.

Examples:

1. I do not think I should complain so much.
2. I do not think I should attend that event.
3. I do not think I should borrow more money.
4. I do not think I should doubt you.
5. I do not think I should decide until later.