The market was shocked -- shocked! -- the Greek debt deal might not go through and suffered its biggest one-day loss so far this year. So if your stock happened to strap on a rocket pack and go higher instead, resist the urge to high-five everyone in the cubicles next to you.

Smart investors won't celebrate until they know that upward leap in their stock was justified. Without a fundamental basis for the bounce, these stocks can quickly make the return trip down.

Is now the time to lock in profits, or is this just the first step toward even higher valuations down the road? Let's examine two stocks that just hit the afterburners, and see whether they're truly headed into orbit.

Stock

CAPS Rating (out of 5)

Tuesday's Change

Harvest Natural Resources (NYSE: HNR) **** 23%
Monster Worldwide (NYSE: MWW) ** 10.6%

Source: Motley Fool CAPS.

The Dow tumbled 203 points yesterday, or 1.6%, so stocks that went appreciably higher are pretty big deals.

A ripe harvest
Gettin' while the gettin's good might be a wise choice for oil producer Harvest Natural Resources, which is looking to sell its assets in Venezuela. With a spotty history of receiving payments from its government-owned partner, no doubt Harvest feels it's best to get out of Dodge before Venezuelan strongman Hugo Chavez comes and just takes what he wants.

It's not like he hasn't done it before. ConocoPhillips (NYSE: COP) and ExxonMobil, wanted $20 billion and $12 billion in compensation, respectively, when their operations got nationalized; Chavez wants to pay Exxon only $255 million. And Cemex (NYSE: CX) saw its operations, along with those of Lafarge and Holcim, taken from it during a wave of nationalization of the cement industry.

Over the past decade, Chavez nationalized private steel companies, took a glass-making plant from Owens-Illinois, and expropriated businesses in telecommunications, energy, agriculture, and finance.

Although no price tag is set yet, talking -- Harvest has thought about this for a while -- gives investors hope. It's good enough for CAPS member line70day, who looks forward to the oil producer leaving the dicey political risk behind, and likely the majority of the investor community, which overwhelmingly believes it can outperform the broad market indexes.

Add Harvest to the Fool's free portfolio tracker to see whether it can extract a pretty penny for its assets before they're devalued by fiat.

It's deja vu for this monster stock
Online employment agency Monster Worldwide moved higher yesterday on a different kind of takeover news, specifically the possibility it might sell itself, spin off a division, or some other "strategic alternative."

Last week, the stock shot higher after the CEO announced the company was pursuing such alternatives and yesterday it was up again when Monster said it had hired financial advisors Stone Key Partners as well as Bank of America's Merrill Lynch to carry out plans. It's good news for investors, as Monster, though the industry leader, has been losing share to a host of rivals including Gannett's CareerBuilder and social media firm LinkedIn (NYSE: LNKD).

Last month, CAPS member neilepi found that its marquee name coupled with a historically low stock price made for an opportune investment: "Solid franchise. At what appears to be a 10-year low or thereabouts this has to be about as good an entry-point as you are likely to get."

Tell us on the Monster Worldwide CAPS page if you think there's still a monster opportunity here, then add it to your own watchlist to see which alternative it ultimately pursues.

Going into orbit
These two companies may have divergent futures despite their short-term bounce, so check out for free the one stock The Motley Fool thinks will break all the rules to win. Hurry, though, because the free look at the new report "Discover the Next Rule-Breaking Multibagger" is available for a limited time only.

Fool contributor Rich Duprey holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool owns shares of Harvest Natural Resources, LinkedIn, and Bank of America. Motley Fool newsletter services have recommended buying shares of ExxonMobil and LinkedIn. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.