Good job today! ;)

sorry, but it would be really better to understand it like this: 고생하셨어요 = honorific + polite; 고생했어요 = polite only. you better always use honorific + polite when talking to strangers, to people older than you are (even if you know them well) and to people with whom you have developed rather formal than friendly relationship. you not only are expected to be polite with them, you are also expected to show your respect toward them, and it will be considered rude to use the polite form only.. in order to make a polite form honorific just add -시- before the polite form ending and decline it according to the common rules: 고생했어요 = 고생하 + ㅆ +어요 ---> 고생하셨어요 = 고생하 + 시+ ㅆ +어요 = 고생하시+ ㅆ +어요. well, maybe it wasn't the question but as it really can cause some problems when used inappropriate I felt like its better to mention that than not to mention ~~

고생하셨어요 is an extra polite form. The simpler form would be 고생했어요 without 셔