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.
As you grow together, remember to keep doing the things you did the first year you were dating
I realised over time that not all conversations are meant to be discussed logically, some are purely emotional e.g my partner feeling jealous when i speak with a girl is an emotion and I shouldn't try to explain it logically. This change made things so much easier for me.
Understanding where my hurt or fear or neediness came from was the first step in helping me strengthen our relationship. Getting to know myself better really helped me feel happier in our relationship, including the hopefully passionate, exciting, challenging, and rewarding life-long relationship with myself and my partner.
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.
As a couple, staying friends has always been important for us, so we have a lot of simple rituals that help us stay that way. E.g together we write inspiring, funny, and uplifting messages on sticky notes and leave them in unexpected places around our community.