Whitney Tilson says that with the stock market up some 75% from its March 2009 lows, it’s time to “grind it out” and wait for opportunities to “be greedy”.

In an interview with Forbes.com, Tilson says that a year ago the market offered investors “perhaps a once in a lifetime great opportunity to be aggressive and play offense. And if you had the courage and the cash, it was an all-time great opportunity to make money.”

Now, things are different. Tilson says he doesn’t think stocks are in “bubble territory”, but adds that “most of the time as an investor you want to play defense, grind it out, and wait for opportunities to be greedy. A year ago was one of those opportunities. Today is not, and so we’re grinding it out.”

He says his firm is focusing on safe plays like Berkshire Hathaway and Microsoft.

“They’re not screaming cheap, but they’re safe,” he says. “They offer nice upside, limited downside. That’s how you grind it out and make decent returns. And then be patient and wait for those opportunities to really get greedy. We’re playing defense now.”

Tilson also talks about how being greedy doesn’t mean trying to call a bottom. “It’s impossible to time the bottom,” he says. “For example, we started buying things in late 2008 after Lehman collapsed and we thought things were cheap. It turns out we were right — but the stocks we were buying got much, much cheaper. It was incredibly painful and difficult to see things we bought at $8 that were at $2 four months later.”