I would like to hit the "like" button on your reply repeatedly.
It is my mantra: recordkeeping, recordkeeping, recordkeeping!
I keep a tiny notebook in the side pocket in my car; every single time I get gas, I note where, the date, how much, the cost, and my mileage off the odometer.
To support this bare-bones diary, I keep the first page of the shop (CPI, assignment, whatever -- the page with the shop's address/phone number), stapled to the receipt/business card/POV for the shop, in a box. Each year in one box. If IRS wants to know why I was in ONeill NE on 3/29, I have the CPI and receipt to prove I was there 100% on business. And I can put my hands on the physical record in about 15 seconds flat.
Having the mileage deduction kicked back because of lack of records is a royal PITA, and it's so incredibly easy and sensible to keep these current records.
When I personally mentor a new shopper, I always gift them with a tiny notebook; I put the first entry in it for them.
Not one -- not a single one -- has ever followed through and kept the notebook up to date.
Which disappoints and dismays me.
Maybe I'm just weird -- I ENJOY record-keeping!