Because I was with my old employer for a long time, my 401k balance never really went down. In addition to the strong market, my contributions plus company match meant it grew almost every month. In terms of asset value, it is my largest account.
After leaving, I moved my 401k to a Fidelity IRA. Because all my new contributions are going into the new 401k plan, the IRA doesn't have the benefit of additional contributions to make it appear to grow.
After tanking with the market (and causing me angina), the runup in the market has pushed the account into positive territory.
During the downtime, I had to fight the urge to sellout and go to safety. Emotional investing is the path to ruin.