"It isn't you. It's adolescence. Even Microsoft, Starbucks, and Google were teenagers once. They faced the same difficultiees you now do. And they survived." --No Man's Land by Doug Tatum. 

Ah, adolescence. When your company (to borrow another phrase from Tatum) is too big to be small, and too small to be big. One bummer of adolescence is that some team members--reliable and loyal from day one--are not the right people to grow you to the next level.

Nor are they ideal fits for a fast-growth culture.

The consequence? You need to make a key firing or two. Here are three steps that will help you:

1. Codify your culture throughout your organization, from job descriptions to performance reviews. 

If cultural mismatch is the main reason you want to dismiss an employee, you need to avoid vagueness in explaning the mismatch. You don't want to say something "like 'This isn't a good fit' or 'It just didn't work out.' That's not strong enough, and it's not quantifiable," notes employment lawyer Joel Greenwald in a recent post on strategy + business.

But if you codify cultural fit into your human resources processes--recruiting, hiring, onboarding, evaluating, retaining--you'll turn your culture into "both a sword and a shield," writes Greenwald. You'll have spelled out your culture, rather than letting it just "be" as something intangible. The more you've spelled it out (and evaluated what it means to be a fit), the more you'll have a leg to stand on if you need to sack an employee who is not a fit. 

2. Emphasize the employee's long-term success.

Explain how they'll be happier elsewhere. Gary Swart, CEO of oDesk, a rapidly growing company based in Redwood City, California, tells the story of a former employee who ultimately was grateful for his termination. "He got to the point where the pressure was on; he had to perform," Swart said. "I would show up at 7 a.m., and he was already in the office, at his desk, cranking away. He was running--just to try and keep up. And he begged us. He said, 'Please, I don't want to leave. I love the company. I'll do anything. Can I intern? Give me a different job. I'll prove it.'"

Swart fired him anyway. Six months later, the former employee invited the CEO to lunch--at Google headquarters. "He got a better job," Swart said. "It was a much better fit for him." The two now have lunch every six months. "He says, 'Thank you. It was because of you--you helped me get into something where I could be more successful, where I could be happy.'"

3. Help them find a job or pursue a path where they'll be happier. 

In Swart's case, a grateful employee returned to thank him for the dismissal that spurred the search for a better job. You can go one step further: You can help an employee find a better position elsewhere. This is more common than you might think: According to a recent poll by the SmartBlog on Leadership, a whopping 67.5 percent of business leaders help by making introductions or offering guidance.

If you're too hard-boiled or old-school to help anyone leave your company, consider what you'll gain. For one thing, your current employees--seeing your kindness toward the almost-departed--might be less hesitant to speak out about their dissatisfactions. In the long-term, this will help your organization improve its retention practices. And imagine if departing employees gave you, say, six months notice instead of two weeks. That's bound to make the transitions all the easier.