二度寝しないのっ！
Don't go back to sleep!

寝不足は体に悪い。
Want of sleep injures our health.

最近、寝不足だ。
I haven't been getting enough sleep lately.

僕は寝が足りない。
I don't get enough sleep.

寝不足で、眠い。
I'm tired from lack of sleep.