Men
We regret nothing. Our oath was made in haste and we shouldn't be held to it. Given that we heard the Elves and Men won the battle without us, it hardly mattered that we didn't fight with them. Yet Isildur's curse didn't depend on the outcome so it still stands. But we're not afraid of him: we don't believe he has the power to curse us. However, he made no promise to leave us alone, so we keep to ourselves for fear of retribution. Now no one bothers us and we bother no one. And no one suffers for it.

Dead Men
It was a blessing, not a curse. Isildur punished us in his anger, but we broke our oath for good reasons and now we've been rewarded. We still die, just as all Men do, but we continue to live afterwards. It's not the same and it took us some time to get used to it, but it's still life, even if we have to die to get it. Now it means we can do whatever we want, for there's no longer anything anyone can do to us. And they're too afraid of us in this form to try very hard.

Ghosts
Everything we thought before was wrong. It's a living death, not life. All we can do is wait and endure our own company. Anyone who comes near is scared of us and we love it and hate it. If only there was something we could do to change our fate. Isildur said we would be asked to fulfil our oath one day and we never thought we would want to. Now we wish we could, but can't believe that day will ever come. Already it's been several lifetimes and nothing has changed. This punishment is too harsh. We regret everything.