Wide awake with 目が冴える
神経が高ぶって、眠れなくなる。また、眠気がなくなる。
Unable to sleep due to heightened nerves. Also, to become no longer sleepy.
Goo Dictionary
The expression 目が冴える literally translates to “the eyes clear” or “the eyes become sharp”, but it is used figuratively to describe a state of mental clarity, alertness, or sharpness. It often conveys the sense of feeling awake, focused, or having heightened awareness, typically in the context of being more awake than usual, like after a good rest, a cup of coffee, or when one is extremely alert and energized.
Examples
好きな子がめがねを忘れた » Volume 8 » Page 21