The only thing stopping your manifestation is you. If you get in the right state and then drop it, it has to come. If you aren't in the right state and drop it, it will never come.

Your state is what you feel to be true. So if you feel true that <put whatever you want here> is already a done deal (not will be done in the future, but is done now) and you feel that way consistently every time you think of the thing you want, then you are in the right state and only then can you completely drop it. I like using Amazon as an example. When you made your order, you know it's done. You don't have it physically yet, but you don't stress about if it will arrive and when and the when mostly doesn't matter that much anyway.