Imagine you’re on the side of a sheet of ice, and no friction. You’ve got a puck that you shove in the direction of the middle of the sheet of ice. Once it gets to the middle, it won’t miraculously stop. It keeps going.
The same is what you’re doing with your sprite - you’re giving it a shove in a direction, and it will keep on moving, forever.
Instead, try updating the position of the sprite to MouseX() & MouseY() with no conditions. It’ll place the sprite at the mouse position. Like: