Once our music teacher asked us all to drop our bows (e.g. violin bows) on the floor. That was to overcome the fear of dropping them, so that we could hold them with relaxed hands. The equivalent for you might be to purposely relax for a while until you miss something (relatively minor) or purposely refrain from capturing something, in order to demonstrate to yourself that it isn't a big deal.
Lucy Palladino's book "Find Your Focus Zone" has some tips for overcoming anxiety
among a lot of other tips for getting into the right frame of mind for optimal
I use a wristwatch which I can set, for example, to beep 2 hours before a dentist appointment and display "dentist". I have a reminder in my system 3 times a week to look over the next few days in my calendar. Etc. I tell myself "So I don't need to worry about anything else for the next few days."
You can try to get a sense of perspective. Suppose someone is dying and you're at their deathbed. Which would be more impressive to hear? "Ah, I've had a satisfying life. I've managed to get through the last 10 years without missing any appointments." or "Ah, I've had a satisfying life. I've had fun, had adventures, made mistakes and laughed about them afterwards with the people I care about."
You can list a small number of things that are really important, and tell yourself that
everything else is minor. For example: my children are alive. Anything else I don't really need to worry about.
You could make reducing anxiety a project, sign up for yoga classes, read books like "Kitchen Table Wisdom" or those "Chicken Soup" books etc. (I haven't read these). The most useful might be to separate out times when you're supposed to be thinking up things to capture and times when you're not, e.g. while swimming. You could spend 5 minutes of every hour doing a mind dump, then spend the other 55 minutes focussing on particular things without worrying about capturing.
If you miss an appointment, you waste someone's time; but if you spend all week worrying about whether you're going to miss an appointment, you waste a lot more of your own time.
"A ship in the harbour is safe, but that is not what ships are for."
Inability is an abstract thing involving comparison with alternate universes; it cannot be experienced.