Some of the most down-to-earth business advice I've heard came from someone often concerned with more ethereal matters: a Catholic priest.

Father James Mallon is pastor of a growing parish in Halifax, Nova Scotia, and the author of Divine Renovation, a book about his experience transforming his church. That was no easy task; Father Mallon had to overcome complaints and resistance from longtime staff members who didn't want to give up responsibilities and attitudes they had held for decades.

Having worked with churches as a consultant, I knew a little about the depth of the challenges Father Mallon faced, and I was curious how he overcame them. What he said was surprisingly, brutally realistic­--and it's advice that should be embraced by all leaders with plans for growth. "You have to go into it knowing that losing people is not just likely, it's inevitable," Father Mallon told me. "As soon as the leader starts the bus and puts a sign on it declaring where it's headed, some people should want to get off."

That's not so easy to accept. There is almost nothing more painful for a leader than seeing good people leave a growing organization, whether it's a priest watching a Sunday school teacher walk out the door or a CEO saying goodbye to a co-founder.

But too many well-intentioned leaders try to keep people from getting off the bus, worried that the departure of a longtime colleague will destroy morale or hurt a friendship. So they accommodate a key employee by creating an unnecessary role, or downplay the true nature of a needed organizational change. In the end, this only prolongs employees' uncertainty and prevents the trans­formation your company must make for continued growth.

Pruning is hard enough when it pertains to employees. But when you see customers (or, in Father Mallon's case, parishioners) drifting away, it's easy to panic. After all, customers are the reason your company exists, and retaining them at any cost seems like an obvious goal. But if you want your company to grow, unnatural customer retention is a terrible idea. I first heard this early in my career, when I worked for a software company that was rapidly expanding, from $100 million to $1 billion in revenue. I'd been invited to attend the weekly executive team meeting, where our leaders were discussing a fundamental shift in product strategy. At one point, the head of marketing said, "Customers aren't going to like this," prompting the CEO to declare, "Screw customers. If we let them choose our strategy, we'll go out of business."

As heretical as that sounds, today I understand the CEO's wisdom. His willingness to try something new, even if it displeased some long-term customers, ultimately allowed the company to attract new business--and propelled it to that $1 billion revenue goal.

So when you attempt to transform your organization and simultaneously retain every employee and every customer, you're sabotaging its growth and health. You're placing a higher priority on avoiding painful conversations than on fulfilling your mission.

That's why leaders of all companies--and especially of those trying to grow--need to go into work every day willing to sacrifice for the good of the organization. You're going to have to let people get off the bus. Sometimes you're going to have to actively invite them to get off.

If you're absolutely determined to avoid those tough conversations, it might be time to admit that you have to get off the bus yourself. But if you can take on the short-term pain of pruning, you'll help your organization grow, and you'll ensure that everyone, employees and customers alike, is stronger for it.