Is it true? Maybe.
I suppose that depends on your world view, but let's go with it. If nothing is forever, is it worth it? In my opinion, absolutely. Sometimes that's the nature of relationships (romantic and nonromantic) they're for a season in life, hopefullly when we need them. Sometimes age or distance or time will cause them to fade, but I find that most interactions with other human beings are worth it because they're the intersection of two meaningful stories. There is something to be gained from being with and learning from another. It'll change you--hopefully, for the better. And most of us could do with a bit a change. It also reminds us that we can love and be loved, which I think many people walk around forgetting.
Naturally, loving leads us to the problem of pain. I think pain is a kind of megaphone. Generally we avoid it. However, pain holds a mirror to fears and insecurities and helps us realize what we think about ourselves and others. I don't go looking for it, but when it's staring me in the face I do my best to wrestle with it instead of ignoring it.
If I had to sum up relationships, I'd put them somewhere in between The Notebook, Eternal Sunshine of the Spotless Mind, Finding Neverland and Little Miss Sunshine. These movies get at bits and pieces of how messy but fulfilling relationships can be. I suppose we each have to decide if the risk is worth it.
And while I'll say in one breath that it totally and completely is, I will also say that some days I wake up and choose to avoid it.