Most of the people I know, if they knew how I "managed" money, would say that I'm horrible with it. I don't budget, balance my checkbook, keep track of investments, retirement accounts, etc. Frankly, I find the attempt to quantify worth sort of offensive and just hate dealing with it - it's just incredibly mundane, tedious, and even just the act or writing checks to pay bills puts me in a mini-funk (until it's over).
But I think that I get along because I just hate being financially beholden to anyone (especially a nameless financial institution). I pay off my (one) credit card each month, etc. My mortgage makes me sick sometimes when I think of how much I owe on it. I think the trick (at least, for me) is to simply not put myself in situations where I'd spend money. I'm a pretty simple person, and other than books, groceries/mortgage/utilities, and the occasional video game or once-a-year trip I spend very little. Just get into the habit of forcing yourself to seriously ask a single question each time you're tempted to make an impulse buy - "Do I need this, and if so, why?" - sure, sometimes the answer will be "no, but I'm buying it anyway", but just asking may give yourself the opportunity to think "well, nah" and pass it by. It seems to help me, anyway.