Relaxation can be learned, like playing a musical instrument, like cooking, like drawing or painting, like kissing.... But it takes practice. And it helps to have guidance from those who know how to practice. E.g., Gay Hendricks "Conscious Breathing" ... or the work of Tara Brach which I mention in the Spirituality and Polyamory thread [Radical Acceptance].
I think breath and mindfulness meditation are the keys to most things.