There's not much glory in handing someone a donut or having to call the Post Office to find out why your employer hasn't received any mail (it's Sunday, but you have to call anyway, just so you can say you tried). You won't necessarily be able to rest your head on your pillow each night content that you are performing a valuable service for a decent, noble, important human being. In fact, very often this job is practically the definition of inglorious. So we hope you've got a thick skin. You're going to need it.