One of the things I always have a hard time adjusting is the budget. Last month I made two trips, in one I spent only 20 USD, but in the other we all spent more than 100 USD, well we were 5 people. I think it was proportional, but we still paid the bill between three people.
My brother went through Bolivia and told me that it is extremely economical. Mainly because of the exchange rate, but the most interesting thing is how you can change those prices in an adjusted way. You always have to look for it, walk, of course, while protecting your safety.
One of the things that has always helped me is not to eat salads or sauces when I am traveling because they can go bad. This also helps when it comes to lowering the food budget (you know you should opt for cooked food). :P
I think that budgeting is an art... hahaha. But that doesn't mean you have to just go through life so badly. And Bolivia, yes, is really cheap and allows you to be quite flexible with your daily budget.
Regarding food, I usually eat a lot of rice, pasta and eggs on my trips hahaha, but every now and then I buy meat and something that gives me more energy!