0 to return to a situation in which you have not seen something -- 回到没有看到（某物）之前
Once you have seen something, you can't unsee it. 有些东西一旦看到，就不可能看不到了。
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
再长的路，一步步也能走完，再短的路，不迈开双脚也无法到达。
