From the May 2014 issue of Entrepreneur

The phone rings. It's Sergey from Google, Marissa from Yahoo or Tim from Apple saying, "I'd like to buy your business … is a zillion dollars enough?" And just like that: The decade of workaholism and takeout food has finally paid off.

Nice fantasy, sure. But here's how things really happen. You get approached by a potential buyer but can't get a straight answer on whether they're ready to put real money or stock against a fair acquisition. Or, the buyer is qualified but you're not ready to sell--and you're terrified that the opportunity will never come again.

Only you can decide what's right for you, but to help you negotiate the dance with a potential suitor or the decision paralysis from having a real offer on the table, here are a few factors to consider from people who've been through it before. Beyond a straight-up time-vs.-money analysis, there are some less quantifiable but equally important reasons to sell.

You have dysfunctional relations with investors. Does your relationship with your shareholders have a positive influence on your life? If not--due to incompatible values, disagreements over strategy or something else--it's time to leave. "When F-bombs get personal in board meetings, it's time to sell," says Jim Franklin, CEO of e-mail service SendGrid. "No one has any respect for each other at that point, and nothing positive for the company is going to happen beyond it."

You've lost interest. David Bloom, co-founder and CEO of restaurant technology startup Ordr.in, says that when he sees founders playing around with new business concepts over beers or casually researching new industries outside of work hours, he knows the writing is on the wall. "That's a warning sign that they've run out of ideas for their current business," he says. "Startup life is all about acting on ideas that are burning to be made real. No ideas--no passion--equals no business. If that's you, it's time to get out."

The market says the time is right. "Selling is like fundraising--it always takes longer than you think it will," warns entrepreneur-turned-investor Sarah Kunst. And if it takes too long, that window of opportunity could shut. "Say it's 2007, and you planned to sell your company 'next year,'" Kunst explains. "Instead, the recession hit, and you ended up struggling to stay solvent until at least 2011, when the economy improved.

"Rarely do you get to decide when it's time to sell," she adds. "Timing the market means looking at other companies' exits in your space to gauge market interest, how much money potential acquirers have on their balance sheets and how the M&A market as a whole is shaping up."

In other words, a reading of your industry's tea leaves may propel you to sell sooner than you'd like--and that's OK. Better to sell a growing company than hang on to one that's plateaued, or worse.