One of my sons lives in Germany. We are here visiting. In my true fashion, I had tried to get him to help me plan out the cost of the trip, to include food, lodging, and travel. He, in true fashion, resisted. 
I sent him some money over the last 6 months to "prepay" the trip. Told him that whatever was leftover, he can have.
Guess what that boy is doing? Every day, we go to back to the hotel, he goes into his room and immediately tallies up each and every receipt into the excel spreadsheet that he made up to track the money.
He still says I have lots of money to spend (my budget was 600 euros, 3 people, 10 days). And he's encouraging us to eat out every day and travel to a different city every day. (In other words, he's not being very conservative about the money!). He got mad when I really wanted to go back to the hotel and eat a sandwich instead of eating out. I reluctantly agreed to getting a bratwurst and pommes...heehehe, the place was closed! So I got my sandwich in a hotel. And those of you who "know" me, you know I grocery shop and eat in the room. Being in another country isn't stopping me! My first stop after getting off the train in his town was to stop at the grocery store BEFORE I made it to the hotel. Serously.
Anyways, just want to say I am a proud mama of my son - he's asking for receipts and keeping a daily tally of what we are spending. AND he's keeping track of the big picture! I am just so proud of him!!
Thanks!
The update.
I was mistaken about the number of days we were/are in Germany - it was 14 days, not 10. Budget was still the same - 600 euros. Ending balance - 400 euros (or super close to it - we will see how it goes at the airport). My son will give me the final tally tonight. Not bad at all.
Lol - one of the funniest things that happened was him panicking and saying I had to help him update the spreadsheet because he is missing some days and he was so sure I had spent money that day! I hadn't. He was actually surprised that I could go all day, several days, without spending money. Really, there was no need to. Bread for breakfast, walk around/travel/sightsee, bread for dinner.
Of course, I am sick of eating bread. 
But it did keep my costs down!
I hope he takes some of these travel lessons with him and continues to be financially responsible.