LONDON -- If you told someone you were staying out of the market until the eurozone crisis and Greek situation became a little clearer, he or she would think you wise to wait. But the late Ben Graham wouldn't.

In the man's own words, "The chief losses to investors come from the purchase of low-quality securities at times of favorable business conditions."

The potential for Greece to exit the Eurozone, along with other market worries, may have given us another opportunity to take the flip side of the great investor's advice. Or, as his star pupil Warren Buffett famously put it, "Be greedy only when others are fearful."

Incidentally, there is a really excellent debate going on regarding the Greek situation on the Fool's discussion boards.

Not many people would describe the current macroeconomic backdrop as "favorable." The FTSE 100 (INDEX: ^FTSE) is reflecting this. At the time of writing, it's at 5,517, hovering around its lowest point this year. In fact, it has lost 8% in the last two months. That's quite a drop.

If you're sitting outside the market waiting for things to unravel and maybe get worse yet, then I think you should think again. Because if the market does fall a lot yet, there will be good reasons to be fearful -- so maybe you'll be waiting again.

Falling prices = good news
So to reverse Ben Graham's advice, it's a good time to purchase high-quality securities during these times of unfavorable business conditions. But which ones?

Personally, I've been buying BP (NYSE: BP) shares at their now lows. I think BP looks a good buy due to its combination of an unfeasibly low P/E, excellent yield, and strong balance sheet. The shares are currently 412 pence.

Meanwhile, my Foolish colleague David O'Hara flagged up five outstanding FTSE 100 shares just last week.

And I've found myself kind of hoping for further falls in RSA Insurance (LSE: RSA.L), currently 104 pence, and Aviva (NSYE: AV), now 301.5 pence. I speculated last week whether RSA's better-than-9% yield can be maintained. I think it probably can. Meanwhile, Stephen Bland thinks Aviva still cuts it as a value share.

The important thing to remember when investing for the long term and for future income is that falling share prices are good news, not bad. But of course, to take advantage of such falls, it's essential to have kept at least some of your powder dry or to introduce fresh cash -- as well as to have the fortitude to hit the buy button when everyone else is fearful.

If you're always waiting for better market conditions and signals that the market has turned, the blue-chip bargains will have gone.

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