Dear EG,
Wow, thank you for offloading the back-story (terrible pun) of this 'terrible, wrong thing' you did. I tend to wholly 'get' what you're saying AND I resonate with the wise words and experiences of Dee, Robby, Haennie on the matter.
Just a few observations:
you spoke of your skiving off home to rest as perhaps 'displacing [your] feelings'. Well, having been in such a situation re work and not being well many many times, I can suggest that instead you were appropriately listening to your feelings. You were in pain and exhausted, wrung out: your body and mind were saying 'enough already! Time to rest'. And instead of dragging yourself through against that inner imperative, you took yourself off home to do just that.
Sure, you didn't tell anyone - and in the context of the (rather silly, arbitrary) 'policy', felt guilty about that. I get that. Indeed, I used to feel guilty even when I'd ring up the office to say I can't come in today, or this morning at least due to illness / exhaustion / mental health day. Much of those times, I'd make my suffering worse whilst lying at home, by writhing in the guilt. Madness!
Even since those days (job ended mid-2009, after seven years), as my chronic conditions worsened - and my alcoholism is only one, it's taking me a very long time to re-frame the sense of 'being useless / irresponsible / not-contributing through working' to one of acceptance. This is what it is, for me now.
In a sense - only a small sense, mind - I've been hearing an echo in your posts of some tendencies you described as Maryanne's during her working life. A bit of drivenness, 'can't stop', 'shouldn't stop', 'must do', 'ought to do', 'should be doing'...that kind of thing. I know I'm putting it too crudely, but maybe you get my drift.
On a positive note, I think Haennie's point about perhaps a bit of up-front collective reform to this 'policy' is very sound. A needed corrective, precisely so that those such as yourself (and probably others) aren't forced into the kind of 'eff it' / flight mode like the other day.