I woke up at four and couldn’t fall back asleep, so I got up at five and, unusually, went for a walk . I woke up at four and couldn’t fall back asleep, so I got up at five and, unusually, went for a walk .

I woke up at four and couldn’t fall back asleep, so I got up at five and, unusually, went for a walk . I woke up at four and couldn’t fall back asleep, so I got up at five and, unusually for me, went for a walk. I woke up at four and couldn’t fall back asleep, so I got up at five and, unusually, went for a walk. I woke up at four and couldn’t fall back asleep, so I got up at five and, unusually for me, went for a walk.

In such a short text, small changes can make a big impact on the rhythm or cadence of each sentence.

I woke up at four and couldn’t fall back asleep, so I got up at five and unusually went for a walk ., which is a rare occurrence. (or: which is unusual for me.) I woke up at four and couldn’t fall back asleep, so I got up at five and went for a walk, which is a rare occurrence. (or: which is unusual for me.)

Outside, it was dark and cold, though I didn’t feel the cold was not biting. Outside, it was dark and cold, though I didn’t feel the cold was biting.

Outside, it was dark and cold, [though I didn’t feel the cold was not biting.] Outside, it was dark and cold, [though I didn’t feel the cold was not biting.]

the second part of the sentence is weak. 1. It's repetitive: you didn't feel the cold and the cold was not biting. (This could be an editing error as you were choosing between two expressions--I've made that kind of error many times.) 2. The first part of the sentence tells the reader it was cold. In the second part you are trying to add more information, but you are using the same word, "cold." One suggestion is to use the word "penetrating" instead of biting. For example: Outside, it was dark and cold, but the chill did not penetrate my thick layers. Outside, it was dark and cold, but I was warm in my .../ protected by my....

Outside, it was dark and cold, though I didn’t feel the cold was nothat biting (or: that harsh). Outside, it was dark and cold, though I didn’t feel the cold was that biting (or: that harsh).

IIn the clear, pure air, the full moon shone brightly in the western night sky. In the clear, pure air, the full moon shone brightly in the western night sky.

IIn the clear, pure air, the full moon shone brightly in the western night sky. In the clear, pure air, the full moon shone brightly in the western night sky.

IIn the clear, pure air, the full moon shone brightly in the western night sky. In the clear, pure air, the full moon shone brightly in the western night sky.