Managing money on the road used to be a big hassle but shouldn’t be anything to fear nowadays.
Unless you’re going in a very remote place, ATMs are everywhere. It’s best to have two cards while traveling, a Visa and a Mastercard. It will be easier if you lost one and some places may only accept one provider. Most ATMs will charge a fee for foreign cards, thus it’s best to withdraw a big amount every week for example.
I keep my money in a money belt which usually stays in the room (if it has a locker). In my wallet I only have enough money for one or two days and one of the credit card, the other one being in the belt.
Ask your banker for credit/debit cards without fees when doing withdrawal abroad. If the ATM asks you if you want to withdraw in your own currency, choose the local one as your bank’s exchange rate will usually be better. Avoid paying with your credit card outside of Western countries as a fee will be applied by the vendor (on top of your bank’s fee).
Traveler’s Check are something of the past, avoid them.
Try to keep some US dollars notes on you. They are the most accepted currency worldwide and can be used to pay for visas on arrival or to get you out of sketchy situation.
To keep track of my expenses on the road, I use the Trail Wallet app for iOS created by Simon from Never Ending Voyage. It’s a bit of a hassle entering your expenses every day but I got used to it and it helps me a lot knowing if I’m on budget.