Not contributing to your retirement: One of the most damaging mistakes you can make is not to contribute to your retirement as early as possible. It is easy to think that retirement is too far away and that you should be saving for more immediate goals like getting a car. But you can sock some savings away in a Roth IRA even if you earn minimum wage while in graduate school. At the very least, start saving for retirement when you land your first job.
The end result: If you don’t have the discipline to save for retirement in your 20s, you may end up spending your entire salary and not saving for a car or anything else either. This is a difficult mistake to recover from that could cost you as much as $100,000 or more in the long run.