Is a really good sign that you need to just have that conversation. Stop thinking; start talking.
The number of times you have rehearsed a conversation in your mind is an indicator for how high the stakes are for either having or not having the real conversation. The length of time you have been avoiding the conversation is the same length of time that slow-but-steady damage has been done by the silence.
Avoiding a conversation prevents important decisions from being made. Avoiding a conversation deprives someone else from the benefits of your communication. Avoiding a conversation stifles truth and honesty, because in the absence of clarity people will fill in the gaps with whatever they think is (or hope to be) true.
A certain amount of rehearsing anything can be good. But eventually it’s time to just go for it. The trick with conversations (especially hard ones) is know when enough is enough. Eventually all the practice will simply do more harm than good.
Less rehearsing; more conversing.