Happiness is although possible to be felt all the time, practically i.e. by considering the life styles of these days and the invariably increasing expectations of people towards each other in the relationships, being happy all the time is not seemingly quite possible for an average minded person. However what can be achieved in every relationship is the togetherness. Happy or sad, easier or tougher, whatever are the times, just staying with each other and working out the things together can work well for any relationship, does not matter how much ever different the two people are. Another thing to be remembered all the time is that no two people are alike in every aspect. Differences are inevitable. And since they are inevitable, they shall not be the reason to think that people cannot sort out the matters together.
Everything is possible provided you have the deep wish and commitment towards each other.