My partner and I have been together 12 years. We met first online and did NOT like each other. I met a friend of his online and when I ran into the friend out in the bars, he became attracted to me.
I thought he was totally out of my league, so I was just myself. The first time we had dinner, I told him all the adventures I have had in life.
I had no idea he was interested for about a week or so.
He invited me along with a bunch of friends to go to Austin Texas for Splash - Memorial Day (for those who don't know - it's the best lake party for the boys in the country). We connected on the trip. Stayed together in Dallas that Monday night and have been together every since.
Everyone has tough times, it is my opinion that you have to find someone with compatible values, ethics and lifestyle. Specifically, spending habits, social habits (btw - he's an introvert, I am very extroverted), religion, cleanliness, family backgrounds and obvious dysfunction (drug habit, etc), then it's just about working it out. Some people do go through major changes that can't be dealt with, e.g. start drugs, etc., but MOST of the time, it's just having enough things to keep you together when you want to FLEE.
We have a business together, house, our families all know each other (at one point neither of us would tell our family we wanted to break up), just need things to keep you together until you realize why you were together.
Be willing to change and accept some things you thought were non-negotiable - because you may find that some of your absolutes become roadblocks to long-term relationship (my bf decided to smoke for a few years - made me NUTS), and finally, remember, YOU aren't always the best person to live with and you have your own shit that you hoist upon the other partner.
All of our friends are together for 10 years+ (one is 25 years) and we all agree that tying yourself up together to get through the bad times, is the thing that keeps us hanging in there.
Jeff's Common Sense Relationship Advice - It's all Free - probably worth that, but there you have it.