What is important in a relationship? It would be intimacy, empathy and affection. If two people are comfortable with the amount intimacy, empathy and affection they receive, then they would feel mostly satisfied. No amount of money or wealth or beauty can substitute for intimacy and affection in a relationship. That's what gives you the feeling of being loved.
Everyone wants to feel loved. Did you noticed that even a small child who doesn't even understand the word "love" yet, he still can experience being loved and cared if his emotional and physical needs are satisfied. People want action of love, not just words. If you both can satisfy physical needs such as protection, affection and emotional needs such as empathy, nice words, emotional support and attention, then a couple would be happy in a relationship.
Relationships are even harder to sustain than a job. Because relationship involves the exchange of love and care and you can't make someone to give it to you they way you want, sometimes it's just given or it isn't.
In my opinion, the most important in a relationship is a trust. Yes, trust is a must. Everything else will fade out, sexual feelings, feelings of danger and excitement can fade out, but true trust will remain forever. If you can find someone who you can trust, this would be the most important for relationship to survive and grow.
Many people confuse trust with being boring, that's why it's so hard to recognize what is true love is at first. If you can find someone who you can trust and sacrifice willingly for each other, then it's all what it takes to be happy. Relationships are hard. But if you both can show enough empathy and protection for each other, then you two can be happy together. Very often men are not very concerned and not very sensitive to woman's needs, some men care more about job or status or survival than his own woman. Women usually care about relationships a think more about them and expect a lot more too than men do, that's why sometimes imbalance grows and can be too late to fix.
But remember, that a priority should be put on trust, on compassion, empathy and security more than excitement. Even that having a trustful relationship is boring sometimes, that's the only base that real true love can grow. True love will come later, but trust should be first and foremost.
Relationship require mutual trust and mutual affection. Exchange of affection builds trust. Where not equal amount of affection is given, then there will be less trust. If you can give each other equal amount of affection and protection, then love can grow and feelings of true joy and satisfaction will grow too.