[atmosx]

Agreed, it is indeed a rather simple mindset: You have to spent less then what you earn. However, that might not be as easy as it seems and hence you need data:

    $ ledger reg Expenses:Personal:Food -b 2016.06.01 -e 2016.06.30
    16-Jun-03 Pita Gyros      Expenses:Personal:Food         € 10.00   € 10.00
    16-Jun-04 Pizza           Expenses:Personal:Food         € 35.00   € 45.00
    16-Jun-09 Pita Gyros      Expenses:Personal:Food         € 10.00   € 55.00
    16-Jun-10 Greek Tavern    Expenses:Personal:Food         € 25.00   € 80.00

Now I know that last month I spend 80€ in food month in fast food which is within my budget for fast-food. If you're not managing a very small amount of money along with a very short list of expenses, then ofc you don't need tools otherwise tools give you data and as we all know, data can be of huge importance.