Should couples be guarded?

Some people think that couples should be intimate. They should have absolute trust in each other and there should be no secrets between them. They feel that there should not be a psychological defense between husband and wife, otherwise it will affect the level of trust between husband and wife and the relationship between husband and wife. However, no matter how close the two people are, they will have their own secrets, and it is impossible to be unprepared for no reason. What do you think? Do you think couples should be on guard? Is there a psychological defense between you and your wife?