Sorry isn't the end of anything. If you mean it, it's supposed to be the beginning that leads to a change. So, the next time you find yourself apologizing to your partner, take a moment to reflect on how you can turn that sorry into a catalyst for positive changes in your relationship.
One thing that has made us very secure in our relationship is truly accepting each other as we are and giving space to each other to be our authentic selves. Obviously, we don't like everything about each other, but accepting these differences without judgment is very important.
Having shared goals and working towards them together has been very helpful in keeping our relationship strong e.g saving for a vacation. Having something to work towards together keeps us motivated and gives us a sense of accomplishment.
When we fight, one of us tries to stay calm and not make it a win-loss ego situation. It doesn't mean don't share your point of view, instead, wait for the nerves to have calmed down.
Giving time to yourself and your partner to adjust with each other's habits, patterns and personality is important for a relationship to grow. No magic happens in one month or few weeks; a relationship takes its own time to cultivate.
I unknowingly started expecting my partner to be a reflection of myself, often asking "why can't you also" when pointing out things I do. But I realized that he brings his own strengths to the relationship, and expecting him to mirror me is not fair or healthy.