Couples in successful, healthy relationships know the one thing they need to do to keep what they have going: generosity. Anyone who has been in a relationship for more than a week has wanted or tried to change their partner. The truth is, we can't change them. That is their job.

The smartest thing we can do for ourselves and our partners is to develop our capacity to love and work off the assumption that successful relationships are always inside jobs.

We have misconceptions about successful couples and assume a relationship is successful because both came from stable and loving homes or have excellent communication skills. Yet, that's not it, it’s not because they lucked out and found a good person to fall in love with, either.

Here are 2 cheat codes that give your marriage an unfair advantage, according to psychology​

1. Practice an overall feeling of generosity towards each other

In other words:

• They make an effort to develop the attitude of "I am on your side" and "I have your back."
• They make a point of being kind and thoughtful with each other, even when they’re angry or disappointed.
• They give each other the benefit of the doubt.
• They assume the best in each other.

This kind of thinking and behavior is easier said than done. Relationship problems are common. It requires a conscious and consistent effort on behalf of both partners. It means paying attention and noticing how things are going between you.

When these things are practiced, they learn how to be kind and generous with each other. In turn, it helps both partners to feel valued, respected, and loved.

Cultivating this attitude toward each other is one of the kindest things we can do for ourselves, as supported by the Journal of Happiness Studies. It puts us in control rather than waiting for our partner to change and allows us to experience the pleasure of giving to someone we love.

This doesn’t mean we take all the responsibility for the state of our relationship and it doesn’t mean we do the internal work for our partners they need to do for themselves. It means we intentionally choose to be kind and generous when it matters the most.

Being kind matters most when they're driving us bananas and we're tempted to react in unhealthy and hurtful ways. When this happens, it can be helpful to picture them hanging onto the edge of a cliff by their fingernails, because that is often how they feel.

Research on emotional regulation and progress shows how people act poorly in ways that are upsetting to us, it is often because they are stressed or hurting. We know when we're stressed or hurting, we temporarily lose the ability to manage our behavior well.

In these moments, when we offer support and understanding, we move closer, build bridges of connection, and have a healthy relationship with each other.

2. Take individual responsibility for working on your part in the marriage

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This essentially means when we encounter a problem or have a disagreement, we look at ourselves first. We look at the way we interact with each other, to determine what we are doing to perpetuate or escalate unhealthy behaviors.

We can only really change ourselves but doing that, of course, is the most difficult of all. Instead of trying to change our partners in a relationship, we can ask ourselves these two important questions:

• "How are my actions affecting our dynamic?"
• "How can we improve the way we interact with each other?"

Then we can work diligently to notice and improve our thoughts and actions. We can work at developing attitudes of gratitude. We can notice and appreciate the positive traits and actions we see in our partners. A study from the Americal Psychological Association on gratitude and romantic relationships demonstrates the importance of actively practicing acceptance, thoughtfulness, and kindness toward each other.

As we get better at loving our partners, it will get easier for them to get better at loving us.

Try these 4 helpful relationship mantras:

• "I will assume the best in my partner."
• "I will practice acceptance instead of trying to change them."
• "I will practice generosity and kindness with my partner."
• "I will look at myself to see what I can change."

Debby Gullery is a speaker and relationship coach with over 25 years of experience coaching and teaching relationship and marriage seminars. She is the author of Small Steps to Bigger Love.