(or possibly make me insane.)
At work I fold many invoices in the course of a month. When folding invoices, I also stuff them into envelopes. I fold the invoices three times so that the address shows through the window of the envelope. I usually grab a stack of envelopes and go to town.
More often than not, I somehow manage to grab a stack of envelopes that exactly matches the number of invoices I have to fold. It’s a very strange coincidence. Or my brain is working on a subconscious mathematical level that amazes me.