Not diversifying your investments
If you are young, you can afford to dabble in stocks and bonds, as you can reap the benefits in the long term. The same cannot be said about someone who is about to retire in a few years. A quick turndown is all it takes to wipe off a portion of your retirement nest egg. As you get older, reduce your investments in the stock market and allocate more towards safer, more stable options, such as bonds and real estate.