Don’t let ser and estar intimidate you! Remember that estar describes temporary conditions (the t in estar is for temporary!), while ser is used to talk about more permanent qualities.
Nosotras estamos muy ocupadas hoy.
We are very busy today.
¡No somos perezosas!
We aren't lazy!
La oficina de Ana está abierta hoy.
Ana's office is open today.
Esta oficina es grande.
This office is big.