how to know if you are a bad employee?

So just from a manager's view point, I love asking questions online from managers so I can get other viewpoints from employee to manager. The last few weeks I've been under a lot of stress with work due to covering for everyone that calls out and always taking extra shifts etc. I'm always on time for work, love going into work, love the people I work with. Today It kind of put it's toll on me because there was a day I requested to have off a week prior to the schedule being released. I get told it has to be put in two weeks in advanced and I understand that. So no problem there. But then a notice was put up on the bulletin board about it needing to be made 3 weeks in advanced. Ok. So now it's 3 and not two. Where'd that come from? I got so frustrated because I've had to cover for my manager and so many of my coworkers because everyone had emergencies. I never put time off requests in, It's so rare when I do. I started to kind of vent to a coworker about it and felt guilty about it because my manager sent me a text asking if everything was okay and to not be afraid to talk if something troubles me. She's very caring and we are friends but it feels so weird. I feel that it is disrespectful to tell your manager things that go on and what you are frustrated with from time to time because you have a job and you have no right to complain. She says how she is so greatful for me and appreciates everything I do and that if I ever have anything i need to get off my chest because we are family and work with eachother 40 hours a week, I need to say something because she wants us all to be happy. Why does this scare me for some reason? Is this a bad thing or something pointless I shouldn't worry about? we are also a small company of 7 workers. I just feel like I made a major error because I couldn't get the day off I needed when I never put requests in and i'm always covering for everyone. But my manager knows that and she says that because I never complain or talk about things to come to her as long as it's in a respectful way.

A good question and depending on the day and my mood the answer can differ widely.

On bad days: Are your breathing? Good, get to work

On normal days: I need you here on time, on schedule and with a smile or at least a non-pissy, chip on the shoulder, world owes me attitude.