“Shoulds” are problematic in relationships. They indicate that a partner should act or not act in a particular way. If a partner doesn’t act accordingly, then an individual judges their partner for behaving inappropriately.
For example, “You should have talked to your boss about getting a raise.” If the partner doesn’t do this, he or she is being judged for not already doing this. A good replacement for “should” is “I wish. . .”, e.g., “I wish you would talk to you boss about getting a raise.” In this way, one expresses their wish without judging.