Learn English – Asking something “just for general knowledge” – acceptable idiom

What kind of "activity" is this used for? Housework? Skydiving?

I ask because English does have a similar idiomatic expression for mundane activities. For example, if he's procrastinating, I might tell my son:

Hurry up and get your schoolwork done. Your homework isn't going to do itself.

or:

For the third time, get your room cleaned up! That bed isn't going to make itself.

As another example, next week, my wife might say something like:

We'll need to take the decorations down soon. These Christmas decorations won't put themselves back in the attic.

This is usually said when talking about some activity that is easy to put off, but I suppose it could be used in other contexts as well. For example, a skydiving instructor could use similar language to emphasize the importance of something:

Make sure you pull your rip cord after you jump out of the plane! That rip cord isn't going to pull itself...

Google books returns some results showing fictional characters making statements like these:

• “Well, gotta go. The soil isn't going to aerate itself!”
• “That paper isn't going to move itself, Elroy.”
• “Well, supper isn't going to get itself on the table.”
• “What are you doing? This stuff isn't going to take itself downstairs no matter how hard you look at it,” Charlie commented sarcastically.

Sounds like you found the one you were looking for, but there are a number of other English idioms that also might work, depending on how exactly you are using them:

• "You can't unring a bell" (or perhaps "you can't unring that bell")
• "You can't unscramble an egg"
• Saying something you later regret is "putting your foot in your mouth"
• "Closing the barn door after the horse has bolted" is doing something too late.