I have a 401K loan out right now and I am paying myself back 6% interest. The bad part is I am make more than 6% on my 401K investments, so I am losing money. The good thing is I am paying myself back the interest and not a bank.

The mistake I made is I have maxed out my 401K so when I needed some money it was all tied up long term. I took out a loan and I am now paying it back to myself. I still max out my 401K because it's hard to get to and the smart thing to do, but knowing if I need it I can get it satisfies my financial needs.