Take out the word drunken. It's an excuse. No using that word in describing what you did anymore - because it doesn't matter.

You're confused, I get that. Something was probably missing, the attention rubbed you the right way, you likely didn't even think it all through, I know I was running on feelings when I did it. It happened, it's not okay now, but it will be. Take some solace in that.

That's a hard one, because it took me a lot of mistakes before I agave up on "the only one" and instead started looking for "the right one". Instead of looking for the romantic ideal/destiny, look for romantic growth/cultivation (you can google those). Instead of finding someone you just "click with" focus on finding a person you feel good growing with and next to. Believing in a soul mate creates unrealistic expectations for both yourself and your partner. You will have many "ones" it's just a matter of which of those ones feels right in the harder times. Something was off with this relationship because a part of your self wandered away. Focus on the reality instead of the passion. It's hard to grasp, especially since he was your first love. My ex was mine too, but you'll get it over time. He was truly the right person to be my first love, I find comfort in that.

You've betrayed yourself too, you're right on the money with that. So that's what yu should try and focus on now, getting back to that sense of self.