What does the spirit of plum blossom refer to?

It describes a person who is strong and beautiful without fear of hardship and cold. Take the poem as evidence:

Falling into mud and crushing it into dust, only the fragrance is as old as ever. -- Lu You, "Bu San Zi - Winged Plum"

There are several branches of plum in the corner of the wall, blooming alone in the cold. -- Wang Anshi, "The Plum"

The water is clear and shallow, and the dark fragrance floats in the dusk of the moon. -- Lin Bu (林逋)《山园小梅-其一》

不经一番寒彻骨，怎得梅花扑鼻香。 -- Zen Master Huang Tiller, "Ode to the Opening of the Upper Hall"

Don't want people to boast of their good colors, but only to leave a clear breath in the Qiankun. -- Wang Coronation, "Plum Blossoms in Ink"