It's possible there is no way a relationship can proceed without ever having relationship trouble of some sort. It does not matter if you are married or have been dating for a long time, something will happen. Many relationships are full of trouble but somehow the couple always pulls through.
How do those that have had a long relationship make it work? You can be sure these couples have had their share of arguments and disagreements over time. What they have been able to do is communicate with each other in a way that helps them resolve the issue in a more successful way.
One of the couple may see a problem early on and brings it up to their partner instead of waiting. Waiting to later could be too late because whatever the issue was could potentially be worse and harder to fix. Get to the bottom of the problem right away and work out a solution for the best results.
A couple of the more volatile subjects that can cause problems are money and lack of communication. Money can be trouble before a couple even gets married and many divorces take place because of financial issues. If a couple can work out who will be responsible for managing the money and etc. things could go smoother. It's also important also to be honest about the state of your financial affairs.
Being a good communicator is very important also. Being able to talk to each other and work through a problem is essential. If the two of you are always doing your own thing while home, not spending time together, you start to lose the ability to communicate with each other.