...so I rigged up a nice little drainage system. Can you describe what you did?

1. How can I help it revive? By revive, you mean for it to make more flowers?

I know you're supposed to cut off the spent flowers, but I'm having trouble knowing where to cut, as the flowers are in little bunches. The bunches are called spikes. When the tip of each spike finishes blooming, you can remove the whole spike, but leave the leafy part of the stem below it. Veronica is a perennial. Perennials give the bonus of coming back next year, but the sacrifice is usually that the bloom period for most is much shorter than annuals.

And should I pull off all the droopy leaves? No. If the plant is droopy and the soil is wet, it is being given too much water. If the leaves are droopy and the soil is dry, not enough water is being given.

2. Would it be bad to move it again, to a smaller pot? I wouldn't further bother any droopy plant unless I discovered an issue that required it. A droopy plant is a very unhappy one and further disruption right now might not be the best thing.

Or, would it do any good to add another plant or two to the big pot? I would probably add some type of annual for continued flowers for the rest of this year, but without seeing a picture, it's hard to be more specific.

Thank you for your advice!

Regarding the drainage system, I took a plastic container that was a couple of inches deep, punched a bunch of holes in it and placed it upside down in the bottom of the pot, figuring this would allow for better drainage than the single hole already in the pot. (I also placed window screening over the container so all the soil wouldn't fall through the holes.)

Unfortunately, it was too late for that plant, but I'm trying to learn from my mistakes. In this case, I believe the pot was just way too deep for the plant. I think there was too much soil, which was holding all this water in between the root ball and the drainage system.