Mat:
So, why not just Flash on his endstep, let him counter it. Then Flash again on your next turn? Why use the Pacts at the end of his turn - there didn't seem to be any real benefit to doing so if you were just going to flash again?
I had just Duressed him turn one seeing FoW, Ancestral, Lotus, REB, two lands on a mull to six. I had two Flashes and two Pacts in my hand, so I took Ancestral and planned to go off on my third land drop after I Merchant Scrolled for Mystical ->Summoner's Pact. He had two cards I didn't know (I found out they were REB, Blue Card) when I tried to go off. I was all but certain that he wouldn't be able to fight through the countermagic.
I was also quite rattled from our previous match and the fact that he drew Ancestral in five opening hands; he mulliganed one of them -- we only played four games. Two of the hands had Lotus, and another had Fastbond, Land, Land, Orchard, Oath. Our first game, he had triple counter and Chain of Vapor on turn five (when I tried to go off). I was on tilt (an upgrade from "rattled") from our previous game, and it might have cost me the game, although he would have still drawn the Reclamation he needed.
In retrospect it is easy to see you're right. I was trying to prevent him from drawing the blue card he needed for FoW and didn't want to give him another topdeck with five mana open. I went off on my turn.