A raise is the easiest money to save, because you have never had it. Nothing in your life is built around it yet. The trap is that within three months it is gone, into a bigger flat, a better car and a slightly nicer everything, and you are as tight as before on more money.
The rule I would give is simple: half of every raise goes to saving, automatically, from the first month. You still feel richer. The chart feels it too, because that half compounds for decades.
The same goes for a bonus, a tax refund, an inheritance. Enjoy some of it. Keep half. The chart on this page shows what a slow creep in spending, one percent a year faster than prices, does over a lifetime. It is bigger than any fee you will ever pay.
Two people, twenty and forty years on
Both get the same ten percent raise next year. Ivo keeps half of it. Ana spends all of it, and from there the spending creeps up one percent a year faster than prices.