"It is easy to get married but hard to stay married.And I rarely see genuinely happy married couples. I think it just goes downhill from a certain point."

Err...what is that suppose to mean, Violet? Are you implying that people shouldn't get married then? Of course happiness doesn't stay intact forever but neither does your age, fitness and health levels. What's next? You shouldn't exercise because you're gonna get old at some point? I apologize for coming across as a cynic but your post doesn't make a whole lot of sense. 

Marriage is a work. It bonds two people together and binds them as a unit. I've known of people who've been married for over 30 years and they say they've enjoyed every moment of it. Things are likely to deteriorate like sexual satisfaction (statistically, sexual interest drops down among 90% married couples after the first child is born) but even then, marriage can be a life-long affair. 

You just need to get married by finding a suitable partner.