I was talking to my friend the other night on the phone. Friend is an awesome person, but socially awkward to say the least.
She was all in a tizz because she had accidentally opened her neighbors Capital One bill, because the mailman had put it in her mailbox by mistake.
I told her that it's not that big of a deal, and she should just put a sticky note on it saying it was opened by mistake and put it in their door (it's an apartment complex).
She did not seemed pleased with this suggestion and shrieks, "I don't know what I'm going to do!!!".
You're going to act like a normal 29 year old and give the person back his credit card bill.