Hello, it doesn't matter if you write your own poem. Just play it casually and make some changes, and it will be more real! If you copy poetry, the impact is still quite great! This is the difficulty of calligraphy. A little mistake will affect the whole work!
If you want to write stable words and improve your calligraphy skills, I suggest you use calligraphy practice tools such as calligraphy three treasures, which will make rapid progress and I hope to adopt them!