Spend as much on crap as you can afford

Just don't spend more. Shocking as it may seem, you can be financially responsible and splurge on stupid things.

The $50 doggy vest, the $200 night out, even the $1,000 ski vacation are all acceptable and even healthy expenses IF they come from your disposable income. If they go on your credit card, you're living beyond your means.

Disposable income is the money you have left after you save for emergencies and long term goals and after you pay for your necessities. (income - necessities - savings = disposable income)

The future growth of our economy depends on people buying more unnecessary crap (and/or working less). As an economy, we covered our necessities (food, clothing, shelter) at least 100 years ago. You need look no further than the fact that only 1% of the US GDP is agriculture (and we are a net-exporter of food) to see that we're covering our necessities just fine (source: CIA World Factbook). We're still having some difficulty with the advanced social necessities of healthcare and education, but on the basics of living we're doing fine (with some unfortunate exceptions).

The biggest challenge is figuring out just how much of the money in each paycheck is disposable income. The easiest way to do this is the 60% solution: Keep fixed expenses to 60% of your income, put 10% to retirement, 10% long term savings (house, car, college) 10% to short term savings (health care deductibles, car maintenance, home maintenance), 10% to fun money. If you're going to do this, I would highly suggest setting up individual accounts for each of these (e.g. 60% for fixed in your checking, 10% to your IRA and 401(k) for your retirement, 10% to a brokerage account for long term savings, 10% to a high yield savings account like ING Direct, and 10% to a 2nd checking account and only use the debit card so you can't spend more than you have). By separating your money at the beginning of the month, you know just how much you can spend on crap that month.

The worst thing you can do is adopt an "It'll all work out in the end, so I'll just do nothing" mentality.

I don't follow the 60% method because I have a more detailed budget that I update at the end of every month (see my series Budgeting Made Easy) and I have a much more granular breakdown of my money (I have separate ING accounts for car maintenance, medical expenses, car insurance, etc. - separate post on that later). But I am anal retentive when it comes to most matters of money and I enjoy knowing where my money goes to the last cent.

Bottom line: Spending money on crap is not the problem. Spending too much money on crap is the problem. Limit your spending to your disposable income and it doesn't matter if you buy diamond encrusted trash-bags.