How many mistakes does a person make in a day?

Sadly, I seem to make too many to count and I worry it could cost me my job at the end of the day. I'm not a stupid person, but I make some ridiculous mistakes like scanning a document my VP should have signed but didn't, and sending back to the originator unsigned. I get so frustrated with myself. I'm also not very happy in my role, so I often wonder if I'm making mistakes as a result of this?? Anyone else make really silly mistakes all the time at work?