You keep using that phrase. I do not think it means what you think it means.

Sorry everybody.  This is very silly.  But it would be so nice to get the word out, because then I won't feel someone has dragged their fingernails down the chalkboard every time I spend any time reading comments here.

"Keep(ing) your powder dry" does not mean the same thing as "choosing your battles," or "saving your ammunition from this fight for a later one" or anything like that.

To keep your powder dry means to keep it from getting wet so you can use it to shoot someone. It's an ironic statement of Oliver Cromwell, made on the eve of battle, and in full context it means that we're going to need faith in God, but also a supply of dry gunpowder.

Uhh...
That's all.
Sorry I mentioned it, really.