一个太少，三个太多，两个正好

某天和一个朋友讨论“解决问题”的话题。他也是一名工程师，所以都有很多的experience，idea可以谈论。但最后我们都同意到最关键的两点。

1）narrow down
2）have a rest

第一点很好理解。对于第二点，我抄别人的一段话作为注解。

when you are tired and depressed of doing sth after a long time researching, attempting. Leave it away temporarily, have a rest, ease your mind, then come back again.you will find you are not that familiar with it... and you have to go through it briefly so that you can continue your work, and right this activity may lead you to a way to solving this problem.