Singular or plural idea here?

[Nordic Bill]

What do you say when you wish to distance yourself from an unpleasant experience, leave a clique, etc., knowing that this will be final?

"I've decided to burn that bridge behind me".

or

"I've decided to burn those bridges behind me".

???

We are dealing with a singular idea here, but I do seem to hear it used more in the plural.

Bill

[Tdol]

If I didn't burn the clique, I'd burn a singular bridge.

[reklov]

Have a look what the CALD has to say:
burn your boats/bridges
If you are in a situation and you burn your boats/bridges, you destroy all possible ways of going back to that situation.

[Tdol]

Here, the question is about adapting the idiom to a contet- idioms are not cast in stone and we can change and adapt them for specific contexts. If you didn't have the word 'that' (or 'those') in the sentence, you wouldn't need to adapt, but once you refer specifically to the thing left, then it changes the context.