Be mindful?

Every time I realise my mistakes, I thought:" What was I thinking? Could have been more MINDFUL." Obviously I didn't know I was doing the wrong thing at the time I was doing it. Writing mistakes, sending the sms to the wrong person, do the opposite of what I'm suppose to do etc...I feel so very stupid. I feel my brain's emptiness, unable to turn the way it was expected(by others, of course). I can only see blank. Sometimes I thought it's almost like being possessed. I can't remember what I have done. Not careful enough, they said. I think sometimes it's because I was too nervous or anxious that my brain didn't want to register it. Well, I don't know how to be more mindful in my daily life, unless you are doing stuff you really like, such as playing. Most of the job are tedious, because we just want to finish it. I started to doubt if my condition is any kind of sickness because everyone else seems to do fine with tedious job.