i think what can be the hardest (and yet most fun - confusing i know

) is learning about the other person. How they deal with stress, how they express their love and affection for you, how they respond to different things can be trying, especially if you respond in a very different way. it can be hard to connect. but thats easily taken care if the couple is committed to communicating their struggles, desires, fears, etc...
i know that was one of the hardest things for me to deal with in the beginning of my relationship. in the beginning he was very flirty and very attentive but after a few months he just stopped. And when i asked him why he explained that he was extremely stressed with some stuff going on in his life at the time so he was preoccupied. I didn't even know he was under stress because when he's *really* stressed he doesn't like t talk about it, I just figured he had lost interest in me. Had we not talked about it, that could have meant a very quick end to the relationship. But once i knew what he was struggling with and where he was coming from it made things much easier for me to accept and deal with.
so yeah communication and taking the time to really understand one another is key in good times and bad.