You should not have delayed.
Ood Sigma had said it to you when you'd arrived on the Ood Sphere, but you had failed to understand the real significance of it then. You'd thought that maybe he was chiding you for those final wild little adventures you'd partaken in, after the Ood had called you. You had not understood the depths of what he had meant.
You should not have delayed, but you did.
You were too busy milking your final days, filling them with brief but wild fun; anything to stop you from thinking about what had happened on Bowie Base One. At the time, it had all seemed so justifiable. What man would not try to extend his last days? You are no stranger to death, but to know in advance that the end is very near - that was something new and chilling. You'd needed - wanted - the distraction of more time, thinking it would be harmless.
It is only now that you realise how very wrong you were. You had been so stupid: so selfish, so careless, so very unobservant. You should not have delayed, but you did. It was only when the Ood had shown you their dreams that you'd started to realise what you had done. And now, racing back to 21st Century Earth, you can fully comprehend how ignorant you had been. If only you had answered your summons when the Ood had called, there would have been enough time to stop all this from happening; there would have been time to stop the Master; time to foil the plans of those still loyal to Harry Saxon. But you'd ignored the Ood and spent your time wandering from place to place with no sense of urgency, trying as best as you could to delay your fate. You'd waited until the last minute, until you could no longer put off your visit, until the visions of the Ood were more than just insubstantial and nightmarish flashes of what could have been. By the time you'd finished frolicking around the Universe, the lines of convergence had been drawn and the actions relative to each other had started to take place. What the Ood saw was now in the present. The Master was returning. And now, instead of heading to Earth to stop him, you're rushing there to contain him; to try to catch him. You had been selfish and it had cost you.
Stepping out of the TARDIS, all you can see is remains of the prison; rubble and scattered here and there, police tape cordoning the whole thing off. Whatever destroyed the place had not happened too long ago - a day, two days, a week at the very most - but relatively you're far too late. The Master has gone; the hunt is on.
You should not have delayed, but you did. And now you're paying for it.