Look at what you're buying and how you can avoid spending the money or at least reduce the cost.
If its food, drinks, snacks etc, take food and drink with you where possible or plan to go somewhere cheaper.
Eg Greggs and McDonald's coffee is half the price of coffee shops.
Supermarkets obviously much cheaper for pastries, multipacks of crisps, drinks or ice creams or other on the go food. A supermarket meal deal can be reasonable value and certainly much cheaper than similar food in cafes.
For entry to attractions there's nearly always a discount available so always look for those before walking up to the gate and paying full price.
Or get annual passes and rotate around, eg I've just bought a National Art Pass which will pay for itself in just a few visits to a particular place I would go most weeks if money was no object but I can also use it for free entry for lots of other places. Or there's National Trust or similar.
What sorts of things are you spending money on, that you're looking to cut back on?