You did indeed get lucky to win this one, you gave him the table by surrendering your position. It's very important at this stage, when you only need 1 and you're playing a better player (8-7 spot?) to keep him on the defensive. You cannot directly protect the 14 so that ball hurts you more than helps, if you let him see any bank on it.What I ended up doing, and I know it was not the best shot but couldn't think of what else to do was this:
My thought was that he needs them all and if I could tie up the 2 balls on his long rail or at least make it so he would have to shoot a combo down the rail after he banked the 14 then I may be ok.
He ended up banking the 14 and making it but then missed the 12 down the rail which he could see without shooting a combination. I got lucky to win this one after my shot, but I still don't think the stun shot down to the bottom rail was there.
You need to ask yourself in these positions, "how do I keep the pressure on him and make the 14 still work for me?" If you cannot find any way to make it work for you, you're typically better off removing it. In this case bringing the 12 over to your side, and having the 8 where it is, makes any shot on the 14 very expensive for him and worth the risk.