paralyzed with fear

Dear Brooke, i thought i was doing so well with my emotions , and feelings, just received a text from my bosses that they want to meet up with me after work tomorrow , and i got literally paralyzed with fear and a knot in my stomach. My mind goes into the most negative right away – they are not happy with me,i am getting fired , i have done something wrong, etc . I actually asked for a meeting myself months ago to address a situation that days off are not being respected – both of them have a habit of bothering each other and me with stupid shit , and the delivery method is to be desired as well . I get very upset and my day is ruined.
Meeting never happened and i never insisted any more because i am doing a lot of self coaching and it helps .
like i said – i have no idea what is this all about , most likely something that they are not happy about , but it’s my guess. Regardless, i want to feel OK with whatever it is .
Ran models – unintentional and intentional – does not seem to help much at the moment. asked to reschedule meeting for couple of weeks after tomorrow – need time to get ready – will listen to your podcast on Difficult Conversations , some concepts were hard to understand, be honest with you.
could you give me an example of how would you handle something like that ? thank you Julia