It takes me about 10-15 minutes to establish my current financial position, to reconcile transactions since my last check and to make reliable financial plans for the upcoming days and weeks. By doing this every few days, I can make sure there will be enough money in my account to pay bills (mostly by monthly Direct Debit), keep an eye on any overspending and check that my financial identity hasn't been compromised.
I use telephone banking to get my balance and recent transactions, noting all this info on a dated page in my A4 diary. Then I check the outgoing payments against the receipts in my purse and make notes of all spending. The direct debit payments and regular incomings are scheduled on a wall calendar that I keep specifically for the job, and I tick off planned payments on there as they come and go. Then it's a simple sum to subtract planned payments from the balance plus expected income: the remaining amount is what I know can safely spend when shopping. I usually divide this amount into weeks and keep the weekly figure in my mind to try to avoid overspending. If I do overspend one week, I know I must compensate the next week.
I've been able to lend money in emergencies to friends who were on ten times my income (with less than half the number of children!) in the past, by keeping track of my finances in this way. It's something that people on very low incomes have to do in order to make ends meet and I think this necessity is an advantage, because it's good to spend carefully and to know how much money you've got.
This kind of financial management isn't taught in schools, is it? But it should be - it's one of the most vital lessons a young person can learn, I think.