You are not alone in this. This is one of my biggest struggles too. But I have found a way that I have learned to manage it. It may not work for everyone but it works for us.
Every month 15% of our income goes
automatically into retirement savings. (Read David Bach's 'The Automatic Millionaire' for the importance of the automatic thing.)
Every month we put $250 into a car replacement account. We have enough to buy a new car when there is enough money in that account to pay for it. (At $3000 a year it adds up pretty quickly in an ING account.)
I have all our bills and giving go out automatically right after pay day as well.
Then I pay myself something. We live simply and don't like clutter but every month I work at spending money on an 'experience' depending on how much there is (our income is variable). In February we spent the weekend in Niagara Falls (got half off because it was off season). This month we might do dinner out and a movie (rare things in this house). We try and make it memory building. In the early days I had to really push myself to spend because I was so worried about the future. But as soon as I had a fully funded emergency account, 15% going automatically into retirement every month, was funding the car replacement fund and putting some monthly into the kid's education fund, I knew the remainder was better spent building happy memories.
How do you know when you can afford things? When you have an emergency fund, your consumer debt is paid off, you're saving for the future, and you've saved up for what ever it is you want to buy.
