If you're in a relationship and managed to get past the seven-year itch, there's no reason to be relieved. You still need to get through the 10-year slump and a 30-year divorce peak.

"Marriage is messy and complicated, especially when we share space with another person, tie our finances together, negotiate sexuality and countless other decisions that daily life demands, to say nothing of adding children or stepchildren to the picture," said Harriet Lerner, psychologist and author of "Marriage Rules." "It's normal for couples to move in and out of boredom — or conflict for that matter — at any point in a marriage."

A 2014 Brigham Young University study that looked at marital quality for more than 2,000 women found that happiness and communication between partners decline from the beginning of a marriage and never get better. They hit rock bottom between the 10- to 15-year-mark, but if couples can make it through those years, the conflicts improve by their 35th anniversary, according to the study. Unfortunately, the marriage never gets back to the honeymoon days.

One common issue in a marriage is simply boredom, Lerner said. But when a marriage starts to become stale, the question for the couple is: Can this be fixed, or is it too stale to be remedied?

At the beginning of every relationship, the couple are actively courting each other, looking their best, trying hard to impress. But after being together for many years, this courting takes second place to children or careers, said Seattle-based relationship coach Kyle Benson.

Looking for connection

It all leads back to an older study published in the Journal of Marriage and the Family in 1998 about newlyweds and boredom that's still relevant today, Benson said.

John Gottman, along with three other researchers at the University of Washington in Seattle, set up a lab that looked like a bed-and-breakfast. They invited newlyweds to spend the day, so their interactions could be observed.

Gottman wanted to see them make connection requests to each other. For example, if one person said, "Look at the beautiful bird outside," he was making a request for a connection and wanted his wife to connect and look at the bird. His wife could look at the bird, or she could tell him she was busy reading her book or making lunch or doing something else.

While this might seem minor, Gottman said these small requests for connection revealed a lot about their relationship health. Couples who divorced six years later connected only 33 percent of the time, and those who were still together after six years connected 87 percent of the time.

Losing interest in partner

The biggest problem is that couples start to feel less surprised by each other, paying less attention to each other as time goes on, said Anna Papa, a Texas-based relationship coach.

"You lose interest in your partner and feel like you know everything about him or her," Papa said. While this is a natural progression of a relationship, it can lead to boredom, which could eventually bring about a divorce in more serious cases.

"A real problem arises when one or both people begin to catastrophize their boredom and cultivate an attitude of negativity: Perhaps I married the wrong person; the love has gone out of our marriage; we have nothing in common," Lerner said. Instead, she said, the couple need to understand that a marriage can tolerate a good amount of boredom as well as conflict when there is a solid foundation of love and respect.

Boredom can simply be a sign that couples need to re-connect and pay more attention to their relationship, Papa said.

"Our whole life is about change and learning, and so should be our marriage," she said.

While many couples go on regular date nights, they may be surprised to learn that these date nights could be contributing to their stale marriage.

Arthur Aron, a psychology professor at Stony Brook University and author of relationship studies, said that many couples make an effort to do weekly date nights but tend to do the same dates over and over again. He found that couples who go on repeat dates have less marital satisfaction than those who go on more exciting, challenging dates such as attending plays or hiking.

"When you overcome challenges with your partner by doing things that are new and exciting, it creates a new and exciting feeling in you that you equate with your partner," Aron said. "Doing the same old, same old doesn't do much to change anything."