<human>: Could you distill the essence of the text into 1-3 sentences?

So I have been dating this girl for a few years, and it looks like each time we have a deep discussion on our relationship, I say the wrong thing.

This has happen numerous times before and I could use some help fixing this. 

Earlier on the relationship, I would say the first thing that comes to my mind. Keep in mind that this was our first serious relationship for both of us, so we don't have much experience. This doesn't end well as I usually don't say the right thing to cheer her up. It gets even worse when we fight, as I usually end up saying something I don't mean.  I try  be better and learn to never text when I'm angry and try to calm myself down before replying. 

Now, it seems like I still don't thinks through enough and say the wrong thing. Or like recently today, I over share a little too much and it freak her out. So I know it's a big question, but how does one not say the wrong thing as much?
<bot>: Have a good solid relationship with GF, but I upset the GF when I share something too personal or I say the wrong thing when we are in a deep conversation on our relationship.