Where could you get enough leather to cover the entire surface of the earth? - A question to provoke contemplation

#1

This question has helped me quite a bit in doing self reflection rather than pinning the blame on external circumstances when things are not going well.

Taken from Master Ri-Chang’s Lamrim Commentary Track 120b

Where could you get enough leather to cover the entire surface of the earth? Wearing just the leather of your sandals Is like covering all the earth.
【以皮覆此地,岂有尔许皮,唯以鞋底皮,如覆一切地。】
说就像我们跑在、走路的时候啊,在那个沙、石子充满着荆棘的地上去走一样,你想要那个皮,或者用那个地毯铺起来的话,它不可能,这个大地这么多。欸!现在有一个很妙的办法,用不着这么大、铺那么多,你只要做一个鞋子,把那个厚厚的一双鞋子穿在你脚上面。对不起,你穿了这双很厚的这双皮鞋,跑哪里都没有问题。所以我们现在学忍辱也是一样,你能够这样做到了,就等于把所有的地都覆盖住了。

Similarly, I cannot change external things, but when I can change my state of mind. Why do I need to change anything else?
【如是诸外物,我不能尽遮,应遮我自心,何须遮诸余。”】
所以外面的东西我不可能,应该遮的遮止我内心,而不是遮外头。那从前面一路上面 (p278) 来告诉我们:佛法是内明、内明,所以我们这个地方特别要注意,特别要注意!我们如果说听了这个道理以后,不在自己内心上用工夫,那完全冤枉,完全冤枉掉了,冤枉掉了自己,也对不起我们穿这身衣服。所以这个地方就特别,我们每一个人应该警惕一下!