Write it down or consider it gone.
If an idea comes into my head I will write it down immediately, otherwise, I can kiss it goodbye.
Your brain cannot effectively hold and organise all of your relevant information, a schedule, and most importantly... your ideas.
The harder you try to make it do so, the less room you leave for creativity.
Picture your brain like a sponge, you can pour a certain amount of water onto a sponge and it will hold, but at some point it becomes full and the water leaks out.
Pouring all of your thoughts into your memory means that the majority of them will simply leak straight out.
You forget things, you never get round to something that could have truly benefited you, and you lose all of your creative ideas.
To emphasise the importance of this (in my eyes) - if I'm falling asleep and have an idea or remember that I need to do something the next day, I'll sit up, open up Notion or the notes app, and write it down.
If I'm away from my phone, often I'll say it over and over and over in my head to ensure that it's one of the ideas that sticks, or quite literally rush to my notes before I forget.
It could be gone in 30 seconds, and that's no exaggeration.
90% of my video or business ideas start this way. Same story for my book... I had a tab on my notes that I would add to every time an idea comes into my head, and then I would sit down and add them all to the manuscript at once.
Pass ideas off to paper or your phone, and create space for more to come in.