Every relationship has its ups and downs, and life is unpredictable. I love easily and I think that what I most appreciate about polyamory, and benefit from, is the ability to create loving relationships on my own terms. I don't have to squeeze my relationships to fit into narrow parameters in order to match what society expects from me.
I never played that game well. I was a high school dropout at 17, lived on my own since I was 19, did whatever I wanted with my life and never cared what family thought, was single (and anti-marriage) until I met my ex, got married at 39, always childfree by choice, always rebellious. Still, I was basically booted from my role of Wife, because I didn't fit my husband's expectations. Since embracing polyamory I now get to say, "No more roles for me." I am creating the life I want.
Of course, one can be deliriously happy in a monogamous partnership -- I know that even I can -- but it's all the expectation placed on that sort of partnership that can be hard to overcome. So, for now and into the foreseeable future, practicing polyamory satisfies this need I have to be free to choose and create what I want my life to be, and to love without reservation, in an ethical, honest way. It makes me happy that I can do this, and just feels right for me.