How do they keep it up for so long

I was with my FA for 1.5 years. I look back now and just wonder how he managed to get past all my defenses by being so consistent for so long. We were friends for half a year before we started dating and he showed up for me over and over. He was always deeply open and vulnerable then. When we started dating we got serious fast and I regret it. He didn’t seem afraid of commitment at first with me. He wanted to be serious and exclusive from day 1. But how he managed to keep it up for so long still gives me whiplash. Just consistent effort and care all throughout the beginnings of our friendship and the honeymoon phase - probably a full year. Until I was so deeply in love and felt fully comfortable and secure.

The week he blindsided me we were planning an international trip. I had just come with him to a family funeral and I’m in all of the photos. We had talked about finally moving in together.

Now I look back and I can see the signs of the back and forth FA hot and cold. He would open up about something serious - feel good about it - then want space. I thought it was all normal. Trust takes time to build. It was ok for him to take his time to open up. Sure he wasn’t ready to move in together yet and didn’t know when he would be but that was fine, that takes time too.