What are the most important, the most the critical, and the most absolutely necessary ingredients for maintaining a fulfilling love in a relationship? Spoiler alert: I really don’t know for sure. However, based on my work as a couples therapist and from what I know about relationship science, I have been wondering if I could come up with five—and just five—key principles for making relationships work.In essence, this list is your Relationship Mission Statement. These are the ideas and concepts that will lead you to success, and although nobody wants a relationship that’s run like a business, it doesn’t hurt to think like a CEO about the core values defining how you want to behave on a daily basis.

Why is it so hard to acknowledge your missteps and ask genuinely for forgiveness?

Now, are these the only five things you need for a successful relationship? Absolutely not, and I encourage you to compare my list to others out there—and to your own concept of what it takes or what makes your relationship what it is. But from my experience as a therapist (and as a human), I can tell you that taking these concepts seriously, and taking them to heart, can do wonders for you and your partner.

1. Love Means Always Having to Say You’re Sorry

Apologies get you unstuck, can deescalate conflict, and can allow your relationship to keep rolling forward in a positive way. We are all imperfect, and when you own your imperfections in real way—perhaps even with a little humor—your partner will appreciate the honesty and sincerity.

I have worked with many people in therapy who have a complete inability to accept responsibility for their nasty behavior and to say, simply, “I am sorry I did this,” or, “I am sorry I acted this way.” Often, they spit out something that sounds like an apology, but really isn’t: “I am sorry you feel this way.”

Why is it so hard to acknowledge your missteps and ask genuinely for forgiveness?

One problem with truly owning your behaviors and apologizing is that if we have negative thoughts about our partners’ behaviors, we start to see them as unworthy of an apology. He’s nasty. She’s self-involved. He only likes me for my money. She’s not really that caring. (You get the idea.) Research tells us that these negative attributions about your partner’s behavior are quite detrimental over time.

To have the ability to say you’re sorry—and to forgive—requires that you cultivate more benign explanations for your partner’s behaviors. If you can view what your partner did in a better light, looking at the situation instead of attributing the action to your partner’s innate personality, then you can enter the forgiveness/apology space.

2. Making Love Really Does Mean Making Love

In Tara Parker-Pope’s excellent book, “For Better,” she discusses the importance of physical intimacy for maintaining a good relationship. There’s a great part in the book where she discusses the lessons concerning sex and relationship satisfaction. She writes, “Forget the lesson. Put the book down and go have sex with your husband or wife.”

Physical intimacy is not simply a nicety of a relationship, it’s a fundamental building block of love. We call it making love for a reason. The biology of an orgasm, for example, was carved over the course of evolutionary history to bring people together and solidify their bond.

For adults with jobs, kids, chores and houses to run, there often doesn’t seem to be time for intimacy. Keeping your sex life alive and reinvigorating it as needed is one of the most important things you can do to maintain a happy relationship.

I’ve written a column about having more sex with your partner. Basically, after you’re done with this column, you should follow Parker-Pope’s advice and go get some. (Did I really write that?)

3. To Know Me (and to Value Me, Support Me and Understand Me) Is to Love Me

Relationship researchers, like all good scientists, love jargon, and they’ve come up with a great term when it comes to psychological intimacy: perceived partner responsiveness (PPR). As I’ve written in another column, PPR refers to the idea that you think your partner gets what you have to say, understands how you feel, knows your needs and is available to respond to you when you need support.

In other words, do you perceive that your partner is there for you? There many components that contribute to PPR, including taking time to truly listen to each other and to understand the other person’s point of view or feelings. Good relationships hinge on a high degree of PPR.

My sense is that PPR is sort of like a bank account—if you take a lot of withdrawals without putting anything back into the account, you’ll be broke before long. Couples need to find time together to invest in PPR. Make sure you continue to know your partner, that you continue to value him or her, and most of all, make sure that he or she feels valued and understood.

4. Not Being Nasty Matters as Much as Being Nice

I stole this subheading directly from a research paper on marriage and health, which showed that while hostile disagreements between partners were associated with increases in blood pressure, supportive comments did not decrease blood pressure.

More generally, the guru of couples research, John Gottman, has identified four behaviors that contribute to what he calls the “cascade toward divorce.” Gottman refers to these behaviors as “The Four Horsemen of the Apocalypse” because they signal dark times ahead. The behaviors are: criticism (attacking your partner’s personality or character), contempt (insulting your partner and communicating that he or she disgusts you and is below you), defensiveness (a failure to take responsibility for your actions—see above where I discuss saying you’re sorry), and stonewalling (observed more often in men, this pattern is defined by a complete withdrawal from interactions).

Together, the Four Horsemen are a terrible combination, but we all do some of these behaviors some of the time. Look for any one of them and try your best to eliminate from the relationship.

5. Never Stop Admiring and Inspiring

A classic finding in relationship science is that seeing our partners in idealized ways leads to improvements in satisfaction over time. Having positive illusions about our partners seems to create a self-fulfilling prophecy for relationship improvement because it protects couples from the inevitable pains that are part of life.

Two types of illusions that I think are especially important are admiration and inspiration. In many ways, these do not have to be illusions at all, but it is important to look for aspects of your partner you can deeply respect and for behaviors that can make you feel inspired and elevated.

One key for finding admiration and inspiration in your relationship—and, for building positive illusions in general—is to always look for positive intent. What is most favorable and charitable explanation you can find your partner’s actions? You won’t always see him or her in this positive light, but if you’re looking for the good, you can create something much more positive.

As I prepared this column I asked a ton of people about their own Top 5 lists for relationship health. Most people noted something about “shared values,” which I left off my list but see as pretty important as well, especially around finances, religion and child-rearing.

I’d be very curious about your Top 5. How would you change my list? What are your five most important ingredients for relationship success?