Video thumbnail is a tweet saying:
I hate how I am a "I have an appointment at 4pm so I can't do anything all day" type of person
TLDR set disruptive alarms. This lets you forget about the event until you need to focus on it, instead of devoting attention to keeping it in mind all day to the detriment of everything else.
Video is very succinct and well-edited and I think it's worth a watching the whole thing. He has a good style and has ADHD himself so he knows how to edit for his audience.
Setting an alarm just makes my waiting mode be spent in tense anticipation of that alarm going off and me mindlessly turning it off without consciously registering it