The meaning of cansado changes completely depending on whether you use it with ser or estar. When you want to talk about you or somebody else being tired, you use cansado with estar:
Carlos está muy cansado. Carlos is very tired.
Estoy cansada de hacer lo mismo todos los días. I’m tired of doing the same thing every day.
If a job or task is tiring, you describe it using cansado and ser:
Carlos está muy cansado. Carlos is very tired.
Estoy cansada de hacer lo mismo todos los días. I’m tired of doing the same thing every day.
Debe de ser cansado tener que corregir tantos exámenes. It must be tiring having to mark so many exam papers.