Budget in Vietnam

I keep getting questions about my travel budget so here goes. First I imagine 50e a day with lodging, food and transportation included. Then when I see the gross total and freak out I divide that by 2. That would mean something like 30 days in Vietnam at 25e a day: 750e.
Easy, right? except that I don't have that.

So I have a look at the Lonely Planet guide and came with 150 dollars plus 100 dollars for emergencies. Yes, that's all I have with me. If something happens I can always use my card but since I have to live off my money for a year I don't want to do that.

Because the trip was a bit on the short notice side I didn't use couch surfing but I hope to do that in Cambodia. So I am staying in a 8 dollar hotel in the old town, I eat in the streets, I take the buses that take hours instead of the express ones. Yes, some without A/C.

Another way to save is to take the night bus/train. I will do that tomorrow evening. I am going to spend the next 5 days in a bus, going from Hanoi to the South of the country. I don't even like buses, this is how short my budget is. I will tell you if all this worked.

Another thing that I try to include in the budget is internet and if it's really cheap, laundry (it was 0.20e in my hotel so I figured...).

Despite being on a tight budget I don't want money to be what rules my travels, I refuse to argue with a driver or a shop owner for what is basically a few Euro cents. So not worth it...

For reference:
1.00EUR = 23.705.67 VND(Vietnamese Dong).

1 water = 5000 to 15000 depending on how touristy is the area.