To be able to concentrate on the same matter for a considerable time is essential to difficult achievement, and even to the understanding of any complicated or abstruse subject. A profound spontaneous interest brings this about naturally, so far as the object of interest is concerned. Most people can concentrate on a mechanical puzzle for a long time ; but this is not in itself very useful. To be really valuable, the concentration must also be within the control of the will.
Source: Bertrand Russell: On Education, especially in early childhood, 1926, Pt. 2：Education of character, chap. 14: General principles
More info.： https://russell-j.com/beginner/OE14-060.HTM
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To accomplish difficult tasks, the ability to concentrate is essential. However, obsessively fixating on something in an abnormal way is not necessarily a good thing.
It is said that concentration requires three key elements: (1) intensity (strength), (2) persistence, and (3) spontaneity. Of course, the object of one's attention is also important. Being able to continuously and enthusiastically engage with something you are deeply interested in is a fortunate thing. However, when economic factors come into play, things often take a strange turn. It is not uncommon for people to become unhappy without realizing it, thinking, "This is a time to endure a little (I might make a profit)", and continuing to do something against their will. Of course, if you can do what you love and also gain financial benefits, there is nothing better than that.
Staying healthy forever is difficult. You may have an accident or face a natural disaster. Some people believe they will live a long life, but once they start to think otherwise, their situation rapidly deteriorates. Such cases are not unheard of.
Here again, we can learn a lesson: it may be best to approach life with the mindset that life is short and handle things accordingly, if you end up living a long life as a result, consider it a bonus.
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