I can only note that the past is beautiful because one never realises an emotion at the time. It expands later, and thus we don't have complete emotions about the present, only about the past.
There are two kinds of beauty; there is a beauty which God gives at birth, and which withers as a flower. And there is a beauty which God grants when by His grace men are born again. That kind of beauty never vanishes but blooms eternally.
To the attentive eye, each moment of the year has its own beauty, and in the same fields, it beholds, every hour, a picture which was never seen before, and which shall never be seen again.