How to stay interested and engaged with the story i’m writing?

ever since i first started writing i always struggled with keeping my motivation or interest in the story i’m writing. the reason varies from losing interest in the story to wanting the change the plot entirely. i don’t really understand why this happens every time, cause in my head the ideas are running constantly and i’m making long stories in my head, but as soon as i go to write it down i feel disinterested.

does anyone else here go through this? what are some ways to overcome this and maintain the interest in my stories? any advice is greatly appreciated!