what wecan't afford to lose?how to answer the question。My opinion is that:defferent people have different answer 。
for example, the farm can afford to lose the harvest。
  
the techer can't afford to lost the knowlege。
the solder can't afford to lost the gun。
the actress can't afford to lost the beauty。
  
the writer can't afford to lost the idea。ect。
But, normally and generally,All of us can't afford to lost the time。
  
How long we can live,I think that about 90。But ,what can we do during the 90 years。
Before 20, you shou studay。
  After 60, totally,you don't have the ability to learen something。
20-60,You have to work hard for life。

So,what we must pay more attention to is the 20。
   Let analysis the 20。
0-6, you don't know how to learen。
6-12, you are happy to learen something。
12-15。
  normally you don't like to studay。
15-18,you have to study hard for the university。
18-20,in my opinion ,you occasionally waste the time。
  
  

Now, let's calculte ,How many years did you learn。I think the total numbers can't higher than 12。

So,My oipnion is that we can't afford to lost time。