Perhaps the issue is specifically that you need to learn (or relearn) how to sit with silence and inactivity, doing absolutely nothing, and shutting down your mind. You’re so used working and completing tasks that your body and mind is constantly active, and so when you have downtime you’re not used to letting go, and as such want to return to this habit because the opposite feels like a waste of precious time, and associated with laziness. At least that’s what I assume, feel free to correct me if i’m wrong.
A real life person I know is exactly like that, addicted to physical and work activities even (and especially) on vacation. Said person tried to relax and do nothing but can’t because said person feels that something MUST be done and should be done now and not later.
If the issue is about others giving you constantly stuff to do, you can simply say no (if it’s that urgent they’ll do it themselves), or have a mutual agreement that you will do X and Y thing but they will do A and B thing (so that you don’t do everything yourself in your free time).
Alternatively, and most importantly, meditate if it’s not already a habit with you. Daily. It specifically trains you to quiet your mind and anxieties and teaches you that peace can be achieved inside ourselves, doesn’t need to be an expenditure of high effort or money, it makes you more relaxed, connected with yourself. And that doing nothing can be also extremely peaceful when done right.
Meditation is the cornerstone in any practice of magic by far in my opinion. When you shut down your mental using meditation (though meditation, like all things, requires practice and frequent sessions to form this habit), you cease to stress about everything for some time, and it sounds like it is what you need. And it is only one of the many benefits of daily meditation.
There are many, many ways to meditate, both eyes closed, or with open eyes (I find those ones easier for those with high mental chatter). Once you learn how to meditate frequently, you’ll be able to enjoy free time normally again without the same chatter even outside of meditation sessions, at least I believe so.