If you would have to ask me right now what the most accurate sign would be for a successful relationship it would have to be communication. Successful communication. Communication where all the parties involved would be honest and true to their own opinion.
Even though it sounds rather simple there are a few things we need to remember when we attempt to communicate, as successful communication is some thing that I have found to be quite rare. The following serves as a quick-and-dirty guide:
Communication require a sender and a receiver. And that is pretty much it. The problem is that we are so caught up in either being the sender or the receiver all the time, that we forget that there has to be both for communication to take place.
Communication require a clear message. Clear as in honest and true, not clear as in "my mouth is moving but I'm thinking of something different" or clear as in "I'm only saying this to you because I know this will make you... whatever" or "I'm saying this to you because I... whatever". Clear as in honest and true. Communication require a clear message.
Communication also require a receiver that understands the medium of communication. It does not mean that there is any communication if the receiver does not understand the language this carries the message. It does not help if you are sending all the right signals if both of you went to the same signal school. Or at least a signal school where the same curriculum was being taught. In fact, the best option would be if both of you were in the same class. Communication requires a receiver.
And it is important that the receiver reply in the same language what he or she thinks in reply to the message, and that the receiver reply with a message that is honest and true.
If that happens continuously for more than one reply, successful communication takes place, and continues until one of the messages isn't clear and true, or until the receiver doesn't understand, or try to understand the message. Communication therefore continues until a message is lost or invalid.
These rules are only valid while both parties remain emotionally detached from the subject they are discussing. But that is the subject of a totally different article!