The causes of suffering and happiness arise from our perception of the thing/matter/issue/object, and once such perception arises, it will generate emotions such as tension, sadness or satisfaction etc.
Therefore, what needs to be rectified is not the ongoing matter. If it is up to the external conditions, then who can stop it from happening? For instance, “I am meditating now, so sky, no thunder please! Peacocks, no hooting please!” How can this be possible? Or, [one would] say, “Don’t rain, for I am walking on the road now.” How could we possibly make the entire universe to become the way I wanted it to be? How could this be possible? Hence, in such an immense universe of ours, human beings, who seem to be endowed with spiritual nature, yet conscientiously feel the sense of insignificance at the same time, how do [we] achieve personal happiness?
Thus, Santideva Bodhisattva stated in his Engaging in the Bodhisattva Deeds that, if you are afraid of the feet getting pricked, some people may choose to shovel all thistles and thorns on the great earth – to remove all prickly items [everywhere]. However, those smarter people will put on shoes, as [analogically] described by “wearing just the leather of your sandals; [it] is like covering all the earth”. By just simply wearing shoes on [their] own feet, it is equivalent to as if one has covered the entire earth with a piece of leather. - Global Lamrim 2, Lecture 0020
How should we apply Santideva’s analogy of wearing leather shoes to alleviating suffering and attaining happiness?