很不幸，在日常生活中疼痛虽然令人很不悦但却是必不可少的。疼痛会警告人们那些可能会伤害到自己的事物来保护他们。 （根据原文的意思疼痛是生活的必需品的而不是避免的，也就是说疼痛本来是对人有很多好处的，你的翻译意思上有点不对。）
PAIN, unfortunately, is a horrible necessity of life. It protects people by alerting them to things that might injure them.
由于是重复使用同一段同步代码，而不是创建自己的同步代码，因此出现的错误会少一些。
Because you are using the same synchronization code over and over, instead of creating your own, you have fewer bugs.
保持清单上的事务尽量的少，你要确保是把最重要的事务完成，而不是压垮自己。
By keeping your task list small, but populated only by important tasks, you ensure that you are getting the important stuff done but not overloading yourself.
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