"Am I making the right decision?"
The good news is that I know that I am. Do I still sometimes romanticize my single days when I was able to go out and get drunk and see where the night might take me? Of course I do. At my bachelor party, I saw my single friends be completely uninhibited, and it looked pretty awesome. But then I think about the other nights of being single. The nights where I would be out, and trying and failing until I just wanted to drink and not get shot down anymore. This doesn't even mention the nights where I wasn't out, and I was playing PS2 just to pass the time and get to the next day. So, yeah, the highs were high, but the lows were just awful.
With my fiancee, I no longer worry about those. There are still highs and lows. And the good news is that the highs maintain longer, because it's out of genuine care for another person instead of a feeling in my penis. And there are still lows, but the lows are because I care, and really, sometimes she can be super irritating. She pisses me off, but the only reason I'm pissed is because I love her.
Also, the key is that the good far outweighs the bad. We rarely fight, I would guess around a half dozen times a year, and when we do, it usually only lasts about an hour until we come to the compromise that both of us (or just me) are idiots. Now that doesn't mean she's perfect. I get irritated with her every day (Why can't she wash the peanut butter off the knife when she's done using it? The dishwasher will not get that off). But we also make each other laugh every day, and it is almost always with the dumbest shit imaginable. If we try to tell people what was so funny, we are always met with the same confused look and response of, "I don't get it."
And that's fine. I don't need people to get us, as long as we get each other. Am I 100% positive that we are going to get married and live happily ever after? No, but just because it's not 100%, that doesn't mean it's not worth going for it. The thing that I feel best about is that things have improved as time has gone on. We started off as friends, dabbled in relationships, then gave real shots to relationships, and the timing just wasn't right. We both matured (me more than her) and realized that we're way happier together than we are when we're apart. That's all I really know. We both make each other happy. And for this sort of commitment, that is the best guarantee that I could hope for.
So, am I going to get married and live happily ever after? I don't know. I'm confident, but everybody is confident when they get married, and half of those people are wrong. The key is that I don't expect marriage to fix things in our relationship. I'm happy with where things are right now; this is just making it official. I'm not 100% positive things will work out, but that's part of what makes it special. It's going to take work, but there's no one I would rather work with than my bride-to-be. Maybe I'm not positive, but you don't have to be sure to still know you're making the right decision.