I had this thought the other day.. to I say certain things that I have been feeling.
I decided to look at what I would be gaining if I said what I was feeling at the time. If anything it would have just made him feel worse and that wasn't why I wanted to tell him.
I also thought long and hard about what my motive was to say what it was. My only motive was to vent and unconsciously I did want to make him feel bad so how is that fair? It wasn't so I didnt say anything.
Not sure exactly what it is you want to talk to him about but timing is also important.