Rush home, check the mail, see it hasn't come, relax for the rest of the day. Repeat daily.

Acknowledge and internalize that there's nothing you can do to hurry up the letter.
Limit yourself to checking the mail once daily, at a time at which you can be certain the mail carrier will have come and gone.
Distract yourself: start a project that will take your mind off the waiting.
Failing that, drink.

yup...once daily, like at 3 or 4 or 5 or 6...don't allow yourself to go check before then. and get out of the house more so you're not nearby.

(or pretend it's Sunday everyday?) ; >

Did you ever stop to think about how much your mail carrier knows about you? Everything he/she gleans from your magazine subscriptions? Notices for overdue bills? Whether you get letters/packages from people? If you have tons of prescriptions delivered? Maybe you're an obvious shopaholic? Did you ever think about that? And now that you are, does it make you paranoid? 'Cause it does me.

I suppose mail carriers see and hear a million tawdry things every day. Like cabdrivers, though, I'd imagine they don't really reflect on them too much after a while.

Why chill? Nothin' wrong with being excited.