Redeemer Presbyterian Church founder and author Tim Keller recently penned a column for The Gospel Coalition, explaining why evangelism is getting harder.

As he notes, many young Christians don’t have a favorable opinion of evangelism. A recent Barna study found that 47 percent of Christian millennials “agree at least somewhat that it is wrong to share one’s personal beliefs with someone of a different faith in hopes that they will one day share the same faith.” That’s higher than Boomers, members of Gen X and Elders (the generation above boomers).

Keller writes that “doing evangelism today will take more patience, courage, and thoughtfulness than was needed a generation ago.” He explains that shifting public ideas about faith—and Christianity as a whole—have made talking about the faith more complicated. And, misdeeds of churches, leaders and high profile Christians make it more difficult to talk about Christianity in many circles.

However, he says despite cultural trends and new challenges, Jesus’ call to tell others the Good News remains unchanged. But, do that effectively, Keller says it will require overcoming three things:

There is a lack of sensitivity—countered by the humility that comes from knowing we are undeserving sinners. There is a lack of courage—countered by the boldness that comes from knowing we are unconditionally loved. Finally there is indifference.

Keller says that training can be helpful, but ultimately, evangelism is about being bold enough to have difficult conversations, and sensitive in our interactions with others.