Every year during tax season I regret it: why didn't I keep my transaction records more smoothly back then?

Now I just treat it as a product requirement, and the core is not to rely on memory to fill in at the end of the year.
Keep a screenshot of CEX deposits and withdrawals, and also jot down on-chain transfer hashes, timestamps, and the corresponding wallet notes—preferably in a flow that goes "where it came from → what I did → where it went."
On-chain data tools and those tagging systems have recently been criticized for lagging behind and possibly misleading, so I basically don't treat them as the only source; I write my own key notes.
Anyway, I'd rather spend ten extra seconds at the time than go crazy at the end of the year.