睡眠问题已经成为很多人困扰的一件事情，睡个有质量的好觉实在是太难了。生活压力增大、早起晚归的生活习惯，造成人们的睡眠质量下降，这样也造成白天的工作没有精力。睡到自然醒、睡个回笼觉，俨然已经成为很奢侈的一件事情。
1. 回笼觉
unprotected sleep
什么叫unprotected sleep?字面上理解是无保护的睡眠或风险睡眠，指的是turning off your alarm clock and immediately going back to sleep; risking not waking up for a job, class, or other daily task. 冒着工作迟到的风险关掉闹钟睡回笼觉，这是不是很多人每天生活的真实写照?
e.g. I'm lucky that I didn't miss my final exam after having 30 minutes of unprotected sleep.
我真走运，睡了30分钟的回笼觉还没错过期末考试。
2. 自然醒
wake up naturally without alarm clock
有研究表明早上被闹钟吵醒容易造成神经衰弱现象，可是试问现在有哪个人早上不是被闹钟吵醒的?当然也有闹钟吵不醒的筒子们。ditch the alarm clock是需要很大勇气的!
e.g. The second school says you should listen to your body's needs and go to bed when you're tired and get up when you naturally wake up.
另外一种观点认为你应该按照你身体的需求，累了之后就睡觉，一觉睡到自然醒。
3. 那些关于“睡觉”的各种短语：
have a cat nap 打个小盹
doze off 打瞌睡
have a siesta 午睡
do not sleep a wink 一夜没合眼
hit the sack 倒头就睡
light sleeper 睡觉轻的人
sleep around the clock 睡了一整天
caught napping 毫无准备，措手不及
e.g. Louis was so tired that he hit the sack soon after supper.
路易斯太累了，所以吃过晚饭就早早上床睡觉了。
e.g. The neighbors were having a party and we couldn't sleep a wink last night.
邻居举行晚会， 吵得我们一夜都没合眼。
e.g. I told my girlfriend that I'm a light sleeper, and that the slightest disturbance will wake me up.
我告诉我女朋友我睡觉很容易醒，最细小的动静也会把我惊醒。
e.g. Their competitors are caught napping while they are responding to complex prospect requirements.
他们正在回应复杂的潜在客户需求，而竞争对手却措手不及。