I have gone through this process several times already and I have a "big dream" that I can't take to fruition just yet.
However, unlike the other ideas, this has also got a plan behind it :) so, my thinking is that you can't get to big goals without going through smaller ones first. This is why I am currently focusing on a much smaller goal but without losing sight of my original, Earth-shattering one :) When it'll finally come to fruition, if it all goes well, it will be so awesome that I will be able to semi-retire :)
Thus, instead of "canning", I would rather say, put it aside, still aiming for the moon, but target getting out of the Earth's orbit first. That's far easier and achievable so - if you can - scale down instead of up. Once you get there, you can review the original plans and ensure they still make sense because, you see, actually accomplish what you want may ultimately show you that your original moonshot was actually a form of waste.
That is why many companies pivot.