Rick and Kay Warren, founders of Saddleback Church, California, will celebrate 40 years of marriage on June 21. At Saddleback's marriage renewal service this weekend the couple also renewed their own vows.

Later, Kay wrote a frank Facebook post about the early days of their marriage in which she said: "We were barely 21, and although we thought we were incredibly mature, we quickly learned just how immature – and broken – we truly were."

She was also honest about the reality of their honeymoon: "we felt intense pressure to have a great honeymoon and a great marriage. The honeymoon, which everyone says is "AMAZING!!!" was not.

"We hardly knew each other... so despite having read the latest and greatest Christian advice books on marriage, sex, communication, children and money, we quickly descended into marital hell, arguing hotly and unfairly about each one of those topics."

Kay added that they put on "happy faces" at church but secretly had doubts about whether they had made the right decision.

"We loved Jesus and we were pretty sure we loved each other – so why were we so miserable? Why did we both secretly wonder if we had just completely ruined our lives by marrying the wrong person?"

She added that divorce was not an option for them but "living a lie" put enormous pressure on them.

Then she said: "Fast forward 40 years. Tonight at a marriage vow renewal service, as I gazed up into the eyes of the young kid I married so long ago, I couldn't help but stand outside of myself and be astonished at how far we two stubborn mules have come.

"Instead of trembling anxiously as we did 40 years ago, this time we confidently held hands and repeated vows of love, faithfulness, forgiveness, grace, acceptance and HOPE – confident because our marriage has weathered some of the worst moments any marriage can endure and left us deeply, deeply loving each other."

She finished by saying: "So to the love of my life, let others have the candy sweet love songs as 'their' song (nothing wrong with that!); ours will always be Huey Lewis' "Happy to Be Stuck with You." And stuck together we are – like the sturdiest, most industrial-strength super glue EVER. Two stubborn mules yoked together with bonds (commitments, vows, pledges, promises, oaths) that hold infinite sweetness."

During the service, Pastor Rick said: "The renewal of your vows is more significant than the first set, because now you know what you're getting into."

Pastor Tom Holladay also spoke at the service about how to have a love that lasts a lifetime. He looked to 1 Peter 1:22, which says "You must keep on loving with all you heart" and shared four ways to do that: to listen and forgive with all your heart, being humble and loving God, putting him at the centre of your marriage.

Over the weekend more than 2,000 couples joined the Warrens in renewing their vows.