It's like this.
When I am the subject:
I have the choice whether to drink the toxin or not in the future (say tomorrow).
If I choose to drink it, I get a million bucks.
If I choose not to, then I get squat.
Whether I drink it or not, in the future, doesn't affect the money.
So, if I choose to drink it in the future, I get the money even if I don't drink it.
The paradox is this:
I choose to drink the toxin today.
A dude gives me the million bucks.
Knowing I get to keep the money even though I don't drink the toxin, I change my mind.
I will now not drink the toxin.

You could say that I never intended to drink the toxin.
I only intended to intend to drink it, so I would get my moolah.
But since I truly didn't intend to drink it, I don't get the money.

It's like when you tell someone that there's no such thing as a selfless good deed.
Then they go about doing things to prove that there is.
They can never prove themselves right, because they are doing the good deed to prove they are right, in which case it then becomes unselfless.