I think the issue is that there are relatively few scenarios where it is actually clear that an attack is imminent, before the attack is present.Oh I realize that.
But I also realize....
You protect yourself first and foremost.
If you are honest and truly defending against a reasonable threat you should have no problem. There is nothing that says you have to wait for the attack for it to be self defense.
It's like that old myth of waiting for them to shoot before you shoot....no....you perceive the attack is imminent and you are in danger....you now can take appropriate actions.