How to think arguments aren’t the end

My bf and I got into not an argument but just a very calm talk about our sex life. There was no yelling, no fighting, no disagreements, just admitting some of our inner thoughts about our decrease in sex lately. He just left I have tears in my eyes listening to sad music thinking our relationship has a dent in it.

We ended up having a great rest of the night and had sex three times and laughed a lot and things were fine but I just felt this overarching sadness. Whenever we laughed together, I just wanted to cry. Idk I just how do I stop being so sensitive to stuff like this? Is this normal of relationships to have?