I don’t mean splash out on crappy souvenirs, but don’t just stuff all 3.5 million Dong into your wallet, or cram 25,000 Rupees in your purse. Put some in your trouser pocket, leave some in your hotel safe, tuck a few in your shoe… If the worst happens and you get mugged or lose your purse/wallet, then you will always have those few notes left so you can afford a taxi back to where you’re staying.