When contemplating whether to use Ser or Estar, I find the best expression to help you remember is 'for how you feel and where you are always use Estar'!Despite both verbs meaning 'to be', ser is used when you are referring to something permanent whereas estar is used when speaking of things that are likely to change and temporary things.
Ser is used for:Descriptions (physical/personality)JobTimeNationalityFamily
Estar is used for:Location/ positionAction (before a present participle)Mental/physical conditions that are temporary such as emotion