It's the hardest part. Best thing to do is let it go all together. Forget the sigil, and forget the intention. At the moment that you charge the sigil and then either destroy or pack it neatly away for good, know that the intention will come to pass, and that you don't need to keep 'waiting anxiously' for it to happen. It's a confidence thing, but also a mental discipline. It's hard to just let something go. For me, all the magic involving ritual, sigils, etc., I do in a space where I have 'shed' my 'waking' self and it all takes place in a separate reality all together. So, it's easy for me to forget what goes on there until I go back there. Something like that is a good idea, in my opinion, because then you don't really have to forget anything in a way.
Other than that, out of sight out of mind. The sooner you forget about it the faster it will work, and with less interference from you while you mill over how you hope the intention of the sigil will manifest. You might consider some kind of negative reinforcement to create a mental block. Snapping yourself with a rubber band whenever you catch yourself thinking about your sigil, for instance, until you brain stops recalling sigil related memories in order to avoid the negative stimuli. Doing something completely unrelated afterwards, as though you'd never done a ritual in the first place is another way - tricky, but a lot of people will do their work, then leave the space and journal about it, or otherwise recall and revisit the experience for a while whether as a matter of recapitulation or just self gratifying "i just did magic" ego-petting. Better to do any journaling before you leave the space and then leaving it all there.
The art of forgetting, aka, letting go, is good for almost all kinds of ritual magic in general. The memory of the ritual is a connection to it, and if you maintain it even after the banishing and closing, if you do such things, you'll still kind of be affecting the ritual itself with hopes, fears, desires, intentions, etc.
Hope that sheds a little light.
The world is complicated - that which makes it up is elegantly simplistic, but infinitely versatile.