This sentence could be understood as: The reason why roses are beautiful is because they have thorns. The existence of these thorns allows roses to show their unique beauty and strength. Just like human beings, having shortcomings can make us more unique and attractive, and at the same time, make us more brave in facing challenges and difficulties. In the face of challenges and difficulties in life, we need a strong will and an indomitable spirit, just like a rose needs thorns to protect it.