Halloween used to be considered the BEST time to make contact with "the other side". It was said that the barrier between the physical and spirit worlds was thinner than at any other time.
Considering that the process of manifesting your desires makes use of spiritual power, it could be said that this is also the best time to do any manifestation work.
One of the key themes in this series is that imagination plays a big part in tapping into your inner Power and directing that Power to manifest your desires.
This could also be one of the reasons why Halloween is considered a good time to make contact with the spirit world, since it's a time when a lot of us allow our imaginations to run wild.
When I was preparing to release my Choose to Believe book, I seriously considered waiting and releasing it around Halloween to create a tie-in with the power of pretending.
The main thing to keep in mind is to have fun with it. If you don't enjoy the process, you won't enjoy the results.
Imagine living the type of life you want, enjoy the experience, and trust that the Power within you will bring it into being.