Christians must learn to measure success by something other than money, fame and power, according to best-selling Christian author Rachel Held Evans.

Evans says in her new book Searching for Sunday, published next month, that as nearly every denomination in the United States faces declining membership and waning influence, Christians may need to find other ways to succeed.

The author, who has become more progressive on issues such as sexuality and left evangelicalism to join the Episcopal Church, calls on Christians to preach "resurrection" rather than success. She also suggests a more sacramental model of church might be the best way forward.

In an extract published on her blog, she writes: "It's strange that Christians so rarely talk about failure when we claim to follow a guy whose three-year ministry was cut short by his crucifixion."

The "fruit of the spirit" is not relevance, impact or even revival, she says. "The fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control – the sort of stuff that, let's face it, doesn't always sell."

She suggests the role of the clergy should not be to dispense information or guard the prestige of their authority, "but rather to go first, to volunteer the truth about their sins, their dreams, their failures, and their fears in order to free others to do the same."

She adds: "Such an approach may repel the masses looking for easy answers from flawless leaders, but I think it might make more disciples of Jesus, and I think it might make healthier, happier pastors. There is a difference, after all, between preaching success and preaching resurrection. Our path is the muddier one."

Talking later to Jonathan Merritt of Religion News Service, she says the way to stop millennials leaving church is not necessarily better music, sleeker logos and more relevant programming.

"Many church leaders make the mistake of thinking millennials are shallow consumers who are leaving church because they aren't being entertained. I think our reasons for leaving church are more complicated, more related to social changes and deep questions of faith than worship style or image."

Attempting to woo them back with "skinny jeans and coffee shops" might even before because millennials have "finely-tuned B.S. meters that can detect when someone's just trying to sell us something," she adds. "We're not looking for a hipper Christianity. We're looking for a truer Christianity.

"Like every generation before and after, we're looking for Jesus – the same Jesus who can be found in the places he's always been: in bread, in wine, in baptism, in the Word, in suffering, in community, and among the least of these. No fog machines required."

She admitted the Episcoapal Church is also in decline with an ageing membership.

"Just about every denomination in the American church is seeing a decline in numbers – including many evangelical denominations – so if it's a competition, then we're all losing, just at different rates.

"I felt drawn to the Episcopal church because it offered some practices I felt were missing in my evangelical experience, like space for silence and reflection, a focus on Christ's presence at the communion table as the climax and center of every worship service, opportunities for women in leadership, and the inclusion of LGBT people."

She also defended the orthodoxy of the Episcopal Church, which is often criticised for its liberalism, even though congregations repeat the creed at every service. And she argued that the New Testament church grew when Christians were in the minority.

"Lately I've been wondering if a little death and resurrection is exactly what the American church needs," she told Merritt. "What if all this talk of waning numbers and shrinking influence means our empire-building days are over and it's a good thing? As the religious landscape in the US changes, Christians are going to have to learn to measure our success by something other than money and power."