How would one translate "I feel rather relieved today. A nagging feeling still looms over me, but on the surface I feel unstressed." Anything to that effect works.
The first sentence could probably be “今天感觉比较放松。” But what after that? For "loom" perhaps something related to “临头” would work, but that gives the feeling that something is really about to happen, whereas the sentence in English more just signifies something at the back of the mind that won't necessarily manifest itself.