I use YNAB but I'm sure any will do. Essentially, I give every dollar a "job", whether that is to be the next car insurance payment 6 months from now or for our vacation fund. I know what money I have and where it's going. I have tracked every single dollar I've spent for about the last 10 years, less some petty cash.
I still have financial insecurity worries that likely stem from my childhood and I doubt they'll ever fully go away (see: people who grew up during the Great Depression), but I can allow myself to spend now and do so confidently.
Well most people with the mentality GP is describing cannot get themselves to do this in first place. not sure if this is a budgeting problem. Ppl save obsessively because they think they might need that money for an unavoidable future expense even though they can't quite tell what that might be.
Maybe collect the unspent amounts into an "Emergency Fun" fund, so you can dip into it if you have a crisis related to fun (gaming device breaks, see something really cool that you want to have or do, etc)
What I'm trying this year is ensuring I can allocate a certain amount to savings (automatic withdrawal) and then treating the leftover money as "free to spend"
I don't know if this will work, as once I see that excess cash I think "Ah, let's use this to pad the emergency fund..." but I need to begin training the mind to be more comfortable with spending.