h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

What I'm fed up with at the moment is the inconsistency.

I have good times and bad times. Usually the bad times are work related, and the good times home related, which makes sense.

Today I had a good morning. I've been asked to go and dep for two days at a different branch, which made me feel really good- it means that they trust me enough to send me. I call up mum and we have a good conversation.
I come back to work after lunch, to have a customer shout at me for asking him if he knew his PIN, more customers than we could really deal with, and then not balancing my till at the end of the day. Plus when I mentioned where I was going for the next two days I discover that this branch has a reputation for being tremendously busy (and I'm going there because they are short staffed), and for not being especially friendly or supportive. One lass actually said she cried the first time she depped there.

It's also triggered a whole can of worms in my brain. I'm worried about me, and my ability to actually work. I lost my last job because I wasn't able to get up the their standards of accuracy. In this job I am still making mistakes. Now, am I just being paranoid? I am still quite new at this, and surely they wouldn't send me to another branch if they thought I was terrible?
The trouble is, is that if I enjoyed what I was doing here, then perhaps I could put up with not being great at what I did (as long as I was good *enough*, of course). But I don't like it particularly. I don't enjoy customer facing roles. So if I don't like it *and* I'm not very good at it, how long can I really stick this out for?

Gah. I don't know. Just needed to get my thoughts on paper a little.