I believe there are only two things that count the most. 

Understanding - This is no surprise that I place understanding as the most important thing which makes a relationship go a long way. Without understanding the miscommunication kicks in the relationship leading to you kicking out (s)he or (s)he showing you the way out. The Miscommunication seems like a very small problem, which you can fix but the fact that with each such hits the relationship gets weaker. You won't be able to see the damage, but it will be there. And as this gets accumulated the relationship comes down. And understanding other person is not that simple, People change with experience. Sometimes it takes up entire life to know a person. So, learn more about your partner and enjoy the relationship. You will be surprised to know how different (s)he is after years together.  

Secondly - Doing things, This is again tied in with the first one but with a lot more of your involvement. _(And by doing things I don't necessarily mean "that involvement")_ it is a common thing that with time the relationship gets mature and to be honest dull. The excitement of running around in the park will not be there and going to the cinemas for some stupid movies. The shopping gets short. And worst of all you start spending time together but not hanging out, Instead you will be talking and planning. Just have the planning and discussion somewhere out. You don't have to run around in the park but still, you can walk and enjoy the atmosphere. This may also seem an easy step but, it is not.  

Trust me this works I learned this stuff the hard way. 
Also, I am no relationship expert so it is entirely up to you on how you want to take my advice. I am just a guy who is in love and gets his ass handed over by her every other Sunday :-)

I am @inuke.
_Greetings from India_