Ruling Initiating an attack accidentally?

[Jahikoi]

Today, I was playing a friendly match with a friend of mine, and I had Flygon out.

I used his Power Swing attack, assuming it would do 80 against Honchkrow that has 80 hp. I announced "I use power swing for the knock out."

After this, my friend said it would only do 70 (due to it being your own bench, not your opponents that add +10) and I agreed that I was wrong.

Then we had a discussion (argument) about whether I should be able to be able to take the attack back. If a player initiates a pokemon power or attack the player is required to continue, but in an obvious case such as this, would I have been able to take the move back?

 

[King Arceus]

It is up to your opponent if they allow you to take your move back.~Mark

 

[DNA]

If you announce any attack - even if you don't have the energy for it - you have to go through with it. If you don't have enough energy, you need to use an attack you have the energy for. In either case, if you want to continue with your turn and not attack until later, you must ask your opponent first.