We can get an inkling of how our mind affects our perception even in our everyday lives. For instance, when we struggle with difficulties, if our attitude is positive, we find that our pain is less and we are more at ease. And we can see that happy people are happy not because of material or external circumstances, but because of the peace and strength of their own mind. The Third Dodrupchen writes:
Wise people realize that all happiness and suffering depend upon the mind, and [so they] seek happiness from the mind itself. They do not rely on external sources, as they understand that the causes of happiness are complete within themselves. If we realize this, then whether we face problems caused by other beings or material things, they won't be able to hurt us much at all.
Source: The Heart of Unconditional Love