它允许我们简化并关注于少量的必不可少的事物。

It'll allow us to simplify and focus on less - on the essential things, the things that matter most.

youdao

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.

youdao

这种将事物划分成必不可少的内容与可有可无的形式的做法增强了UML的可管理性。

This partitioning into essential content and dispensable form enhances UML's manageability.

youdao