Not exactly that, but close. You need to accept that the thing has come to pass and is done, then your mind can naturally move on with life and the forgetting happens.
This is one of the benefits of daily practice that many never consider. When you are doing some kind of ritual every single day, and mixing in the profound ones into the mix right along with the simpler ones, you eventually lose track of what you did, which aids in the forgetting, or at the very least you have cast enough where the result of any one ritual is less likely to be on the forefront of your mind. This is also why keeping notes is important. Once you get good at forgetting you will want to have a reference so you can compare results, techniques, etc, after manifestation.
The same general principle works in my chaos sigil practice. I create the sigil, pre-charge, and put it into a folder until I can’t remember what the sigil means to my conscious mind. Then I let it loose. The results are always incoming, lol, and the surprise is nice.