We learn more from mistakes than success. Psychologists blandly state, Errors are necessary in new learning. An error is where we happily begin. Don't pounce on it, but explain and correct. Don't even call it an error.
Lets do that again.
See if what your child has completed leads you to new activities. OK, you say. Lets go out and find a leaf like the one you just colored. Mark the paper with a reward sticker when the task is complete. Go over what your child has done.