why working with friends SUCKS!

Okay, so my main gaming group in Dayton uses a completely home-grown gaming system called High Adventure.
We've been working on it for 20+years, and it's in its... hell, I don't know... 20th edition (and you thought D&D was bad).
So the group decided to do an Oriental Campaign, and I decided to do a supplement for said campaign.
One of my friends has been the senior designer on the High Adventure project for lo these many years, but he was too busy with his job to do much at the beginning of the Eastern Realms Project, so it was all me.
Last night, he finally found the time, downloaded the second-most recent copy of the book (I'm working in Alabama, so I've been posting the updates so that the boys can get cracking on character design) and commenced to edit the format, make whatever content/ layout changes he felt were necessary, and write the Introduction (that REALLY pissed me off.) And he did all this without even talking to me about it.
Pissed off, yeah. I was pissed off.
It's stupid to be this irritated about a stupid game, but I am.
I had some idea of, once it was finished, converting it for d20 and shopping it around. Now, I just want to say "It's as done as it's getting. Have at!" and wash my hands of it.
But I'm not going to.
I sent him a long email, trying to explain why I was mad (and I'm sure he didn't understand until I laid it out for him.) Then I made comment on his edits. Not too pissy comments, I hope.
It's always been like this with him. I don't know why I thought this project would be different.
The last time we worked on a project together (19 years ago) we didn't speak for 6 or 7 years.
I'm not going le let that happen this time. Older and wiser and all that.
Okay, back to work.