Every year during tax season, I regret it: I saved a few bucks on fees back then, but I didn't keep complete records, and reconciling at the end of the year totally blows my mind... Now I just use a simple method: whenever I make a large exchange/ cross-chain/ claim an airdrop, I immediately export the exchange transaction history, take a screenshot of the on-chain tx hash, and keep a copy, then write a note like "what's this for" (otherwise I forget in a couple of months).

And don't mind the slippage, Gas, tips, or anything else—if you can remember it, just record it; honestly, it's all a cost.
Recently, with social mining and fan token schemes—"attention is mining"—I've participated a few times. It's lively, but the records are even more fragmented. When the day comes to file taxes, you'll see who’s really mining your time...
Anyway, I’ll start gathering the evidence chain so I don’t have to rely solely on memory in the end.