Make a joke about yourself. Be light-hearted. Turn it around. I worked the other night after two months off. I had forgotten everything. Needed a lot of humor and some other stuff to get me through that shift.
Oh.. are you talking about say you give someone her prescription and she says "Where's my change.." and you think "@#)*... " and you don't know how much to give her?
Its happened to me before actually.. twice. Not at a pharmacy but in a job I had in high school, you just have to admit you made a mistake, its a part of any job, you aren't a perfect human being. Admit you made a mistake, apologize, be super friendly. There are ways about doing this.. not sure about in a pharmacy, but there should be a count of how much money SHOULD be in the cash register, you just have to spend the time and count out the money and see if its over 15 dollars.. then you probably owe her 15 dollars, or maybe there is a camera in the pharmacy and you can watch that. Again.. i'm not sure how its done in a pharmacy but thats how we dealt with it. Just make sure to say you are sorry for taking up their time and this is just standard procedure, its not like you don't trust them but you made a mistake and now you have to go through this process.
To allformydaughter: Is that your cat?! That picture is cute and hilarious. =)