1. Not checking your statements. I know I tend to do this, always while planning to look at them later..when I have more time. Ack. Check your statements asap to make sure charges on there are correct, and to see exactly how you have spent your money lately (in case you have forgotten!)
2. Not Saving for Retirement. So easy to put off, but that day will come. Start saving now, and you will have at least some peace of mind!
3. Not Saving for Your Emergency Fund. Same thing as with the Retirement Savings. Budget your money so that some of it goes into an emergency fund. Even a little bit each week will be better than nothing saved for that inevitable 'rainy day.'
4. Not Paying More Than the Minimum on Credit Cards. (Or should we just say, using those credit cards?) Seriously, paying the minimum is better than not paying, but to really make a dent, you need to always pay a little extra. It may hurt up front, but it will pay those credit cards off more quickly, which means paying less interest overall.
5. Not Thinking Before Spending. Impulse buying is a sure-fire way to feel depressed and more broke later. Save the need for instant gratification, and instead walk away from the thing that seems to be calling your name. Go home and think about that potential purchase first. If you do decide you absolutely need/want it, and cannot fathom living without it, then get an envelope marked just for that item, and start saving for it. Sure, you may have to wait longer, but you will undoubtedly be happier when you do buy it, knowing that you saved for it instead of dipping into the money that was meant for, oh say, those credit card payments!