You still end up ahead. [1] Even if you invest at the worst possible times, investing early and over a long period of time will still make you wealthy. This isn't necessarily the case in all situations; I think you would have lost money in the Japanese stock market over the past decade if you don't consider dividends/potential deflation. But it has held for the US market for a long time.

[1] http://awealthofcommonsense.com/2014/02/worlds-worst-market-...