MY FIRST DAY SUCKED!!!

Well today was the day I was by myself all day and boy did that suck. First customer came at 3:30 and amy next came at 5:30. so it was extremely slow. I was positive I did everything right until it came time to cashout and I was $100 short. Where it went I don't know, I'm sure I just entered something wrong but I don't even know where to start looking to find out what. It was probably when I started to day cuz the only time I ever did that was my first day of work and I didn't even post the open. So basically I never did it before. I was/am so frustrated cuz now I have to sit on this mistake till Monday when the store opens and I had to leave a note for my manager that I f***ed up and hopefully she can fix it. The other manager she told me to contact for help was no help at all cuz she couldn't access our computer system. So now I am tired, bored, and very frustrated cuz I am expected to open twice a week and they had better give me more training if they want me to know what to do. There I have said all I needed to say for now, and hopefully this will help put my mind at ease for now. If anyone has some good news I would love to hear about it. Enough dwelling on my bad day I need to hear about something good. Take care all T.