I do a bit of a hybrid approach really. First things first, the day after pay day a set amount goes to our joint account out of which all bills, mortgage and grocery shopping etc are paid, so I know that is covered.
On the same day a set amount comes out of my account and into my ISA/long term savings account each month, without fail (except in dire emergencies). This money is only for specific purposes, e.g. home improvement goals, car replacement fund, rainy day fund.
I also have a set amount which goes into an easy access/unlimited withdrawals savings account which is to cover annual bills like insurances, holidays and Christmas. I have on occasion dipped into this when unexpected things like vet bills or car breakdown occurs but I try to avoid this except where really necessary.
What's left is then mine for spends on hobbies, socialising, clothes, make up, frittering etc. DH keeps a similar amount in his own current account so we are equal. I have found over time that what's left should (in a normal month) be enough to cover my needs, if I am particularly frugal there is sometimes a surplus which I either roll over to the next month (e.g. if I know I need to buy something expensive like winter boots or a coat the next month) or sometimes I transfer a bit extra to the holiday/Christmas funds. As I say, on occasion I've had to borrow a bit from the savings account where we'd have a big surprise bill but in general I manage to avoid this by taking the attitude of once I've spent my monthly budget, that's it, no more spending except where it's completely unavoidable - every £ I spend out of the savings is less money to spend on important stuff like holidays and birthdays which acts as a bit of a brake...
If I get an unexpected bit of income (e.g. payrise at work) or tax rebate, it goes straight into savings.
Can you do a bit of an audit on your spending, go over your last few months spending and try (being honest but not harsh with yourself, it's a not a blame game) to work out a reasonable amount for spends? I wouldn't try and set it unrealistically low as you'll only end up overspending, so it should be an amount that if you are being reasonably frugal you can stick to?