They will probably base your performance on the sick days you have taken and the amount of times you have worked on a day off when crew control has called you. Or...
Have you come into the office and worked for free for the training department or flight ops?
Have you ever refused going into discression or reduced rest?
Have you ever written an ASR or OR that shows the company in a bad light?
Are you the companies bitch?
See it's very easy to asses your performance.