Communication is the key to any relationship. With bad communication, problems crop up at unexpected places. This is a classical case. I am feeling very hurt because of what you said. When did I say that? Two days back. But I never meant that. I do not know what you meant, but it has been hurting me since then. Oh, I am sorry. I genuinely never meant that. Why did you not ask me then and there? I was very hurt to ask. Oh, I am very sorry.
What you say can make a big difference to your relationship. How will the listener know what you mean? The listener only picks up your words and makes interpretation. Choosing right words while communicating is important. If you know about your partners sensitivities about a subject, you have to be very careful while talking even in jest. Your tone has to be perfect and you have to be careful while speaking. You never know when you will hurt your partners feelings. This communication care is very important if the relationship is already going bad and you wish to save it.
Freedom in communication can be taken if you are sure that your partner understands you well and will not take any talk otherwise. In that case, you both behave like close friends, who speak their mind without bothering. If the relationship has not reached that level you have to be careful while talking. Loose talk can spoil a relationship.